Ability to add subheadings / dividers between long lists of stories

https://ombulabs.atlassian.net/browse/DT-255

**Before we start...:**

- [x] I checked the documentation and didn't find this feature
- [x] I checked to make sure that this feature has not already been requested

**Branch/Commit:**

Commit: 432aef33017866df594fca0469d2899dfe803da5

**Describe the feature:**

As an estimator
When I have a long list of stories
I would like to add sub-titles/labels/dividers to
make it visually clearer
and to visually group stories

**Problem:**

As a estimator
When I have a long list of stories
The long list of stories become like a see of text
By grouping the stories it might be possible to convey addition context to the other project viewer.

**I will abide by the [code of conduct](https://github.com/fastruby/points/blob/main/CODE_OF_CONDUCT.md)**