groupBy not working in latest version

Hello folks, many thanks for a very nice work!

I'm completely pissed off groupBy.

I have .grenrc.json (cause there are no examples available how to use yaml):

```
{
"dataSource": "milestones",
"prefix": "",
"groupBy": {
"Bug Fixes:": [ "bug","minor" ],
"Refactoring": ["refactoring"],
"Major features": ["feature", "major"]
},
"milestoneMatch": "(Milestone {{tag_name}})",
"changelogFilename": "CHANGELOG3.md"
}
```

Whenever I call gen changelog --override I have exactly the same output:

```
## v1.0.0 (13/11/2020)
- [**refactoring**] Refactor release path and impact analysis to DTOs [#106](https://github.com/tillias/microservice-catalog/issues/106)
- [**documentation**][**major**] Visual regression tests with percy.io [#103](https://github.com/tillias/microservice-catalog/issues/103)
- [**bug**][**minor**] Clear selection in dependency dashboard after microservice deletion [#100](https://github.com/tillias/microservice-catalog/issues/100)
- [**documentation**] Prepare e2e tests with cypress [#96](https://github.com/tillias/microservice-catalog/issues/96)
- [**feature**][**minor**] Display status and team name for microservice dialog(s) [#90](https://github.com/tillias/microservice-catalog/issues/90)
- [**feature**][**minor**] Edit microservice button [#89](https://github.com/tillias/microservice-catalog/issues/89)
- [**documentation**] k8s deployment scripts [#88](https://github.com/tillias/microservice-catalog/issues/88)
- [**feature**][**major**] Dependency dashboard legend [#86](https://github.com/tillias/microservice-catalog/issues/86)
- [**feature**][**minor**] Swap nodes in create dependency dialog [#84](https://github.com/tillias/microservice-catalog/issues/84)
- [**feature**][**major**] Impact analysis [#79](https://github.com/tillias/microservice-catalog/issues/79)
- [**feature**][**minor**] Build docker image and push from circle-ci [#76](https://github.com/tillias/microservice-catalog/issues/76)
- [**feature**][**minor**] Migrate to circle-ci [#74](https://github.com/tillias/microservice-catalog/issues/74)
- [**feature**][**major**] Duplicated dependencies validation [#71](https://github.com/tillias/microservice-catalog/issues/71)
- [**bug**] Name for target node in release path is not displayed [#70](https://github.com/tillias/microservice-catalog/issues/70)
- [**feature**][**minor**] Delete dependency & microservice using hotkey [#69](https://github.com/tillias/microservice-catalog/issues/69)
- [**bug**][**minor**] Translation for custom validation errors [#68](https://github.com/tillias/microservice-catalog/issues/68)
- [**feature**][**minor**] SonarCloud code coverage issue [#65](https://github.com/tillias/microservice-catalog/issues/65)
- [**feature**][**minor**] Create dependency by selecting multiple nodes [#61](https://github.com/tillias/microservice-catalog/issues/61)
- [**feature**][**major**] Build and visualize release path for particular microservice [#57](https://github.com/tillias/microservice-catalog/issues/57)
- [**feature**][**minor**] Remember start dependency when creating new one [#56](https://github.com/tillias/microservice-catalog/issues/56)
- [**feature**][**major**] Dependency validation [#54](https://github.com/tillias/microservice-catalog/issues/54)
- [**feature**][**minor**] Delete dependency from dashboard screen [#53](https://github.com/tillias/microservice-catalog/issues/53)
- [**documentation**] Update home page and create gitter chat [#50](https://github.com/tillias/microservice-catalog/issues/50)
- [**bug**] Search box looses its content when accordion panel is collapsed [#47](https://github.com/tillias/microservice-catalog/issues/47)
- [**feature**][**major**] Actions menu for dependency dashboard [#45](https://github.com/tillias/microservice-catalog/issues/45)
- [**documentation**][**feature**][**minor**] Try with PWD badge [#43](https://github.com/tillias/microservice-catalog/issues/43)
- [**documentation**][**feature**][**minor**] Custom port for Spring Boot App [#41](https://github.com/tillias/microservice-catalog/issues/41)
- [**documentation**][**minor**] Docker compose for rapid use-cases demo [#39](https://github.com/tillias/microservice-catalog/issues/39)
- [**feature**][**minor**] Feature flags [#38](https://github.com/tillias/microservice-catalog/issues/38)
- [**feature**][**minor**] Add CI link to microservice [#32](https://github.com/tillias/microservice-catalog/issues/32)
- [**feature**][**minor**] Reset search criteria using icon or button [#30](https://github.com/tillias/microservice-catalog/issues/30)
- [**bug**][**minor**] Localization for search box & direction selectors [#29](https://github.com/tillias/microservice-catalog/issues/29)
- [**feature**][**major**] Create dependency from dependencies dashboard [#27](https://github.com/tillias/microservice-catalog/issues/27)
- [**feature**][**major**] Create microservice from dependencies dashboard [#26](https://github.com/tillias/microservice-catalog/issues/26)
- [**feature**][**minor**] Display microservice description in dependency view on mouse over [#23](https://github.com/tillias/microservice-catalog/issues/23)
- [**bug**] Dependency graph is incorrect, missing edges [#20](https://github.com/tillias/microservice-catalog/issues/20)
- [**feature**][**minor**] Setup sonar-qube [#18](https://github.com/tillias/microservice-catalog/issues/18)
- [**feature**][**major**] Search box for dependency view [#17](https://github.com/tillias/microservice-catalog/issues/17)
- [**feature**][**major**] Multi-field search criteria (advanced search) [#16](https://github.com/tillias/microservice-catalog/issues/16)
- [**feature**][**minor**] Generate long-term heroku token for travis-ci [#14](https://github.com/tillias/microservice-catalog/issues/14)
- [**feature**] Better handling of big images [#13](https://github.com/tillias/microservice-catalog/issues/13)
- [**feature**] Improve travis-ci build [#11](https://github.com/tillias/microservice-catalog/issues/11)
- [**feature**] Extract dashboard card into separate comoponent [#10](https://github.com/tillias/microservice-catalog/issues/10)
- [**feature**] Bundle some test images for dev profile [#7](https://github.com/tillias/microservice-catalog/issues/7)
- [**feature**] Microservice custom details component [#6](https://github.com/tillias/microservice-catalog/issues/6)
- [**feature**] Search field [#5](https://github.com/tillias/microservice-catalog/issues/5)
- [**feature**] Configurable data source [#3](https://github.com/tillias/microservice-catalog/issues/3)
- [**feature**] Visualize dependencies between microservices [#2](https://github.com/tillias/microservice-catalog/issues/2)
- [**feature**][**minor**] Configurable image source [#1](https://github.com/tillias/microservice-catalog/issues/1)
```

There is no grouping at all (

Can you please advise what I'm doing wrong?

Reproduce the report with the shown .grenrc.json configuration and the `gen changelog --override` command. Trace the changelog generation entry point and the handling of `groupBy`, then compare the output with the requested category grouping. Done means matching entries are emitted under the configured group headings.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.