Feature request: Include/exclude files/folders

## Challenges/opportunities
GitHub repos often contain files that are irrelevant in a "talk to this repo" context. My experience is coding tools that have full context awareness of an entire repo tend to meander into files that are irrelevant to the task at hand.

## Proposed solution
Provide the ability to explicitly include/exclude files and folders from the summary. That way the text file provides the LLM with a custom narrow scope containing only what is relevant to the task at hand.

## Expanded solution
Option that generates files for each root folder. So for a typical repo you'd get
- `full-repo.txt`
- `[root-folder-name].txt`
- `[other-root-folder-name].txt`
- etc

Could also have a config option to specify how many folders deep this creation should go:
- `[path-to-folder-name].txt`