Add support for clicking on arrows in the file list to expand/collapse directories

[blakemckeany]

PR Description

This PR adds support for clicking on arrows in the file changes list view, so that a mouse can be used to expand/collapse directories. This enhancement was raised here as issue #5088.

This is my first pull request into lazygit so any feedback would be much appreciated! That being said I have tried my best to follow CONTRIBUTING.md and read the relevant docs to ensure all steps are followed.

Please check if the PR fulfills these requirements

• Cheatsheets are up-to-date (run go generate ./...)
• Code has been formatted (see here)
• Tests have been added/updated (see here for the integration test guide)
• Text is internationalised (see here)
• If a new UserConfig entry was added, make sure it can be hot-reloaded (see here)
• Docs have been updated if necessary
• You've read through your own file changes for silly mistakes etc

Result

files-mouse-use.mp4