📝 Add docstrings to `dhruvil/api-improvements-and-features`

Docstrings generation was requested by @mdhruvil.

* https://github.com/mdhruvil/deplit/pull/13#issuecomment-2862948866

The following files were modified:

* `apps/api/src/lib/auth.ts`
* `apps/api/src/lib/github-webhook.ts`
* `apps/api/src/lib/github.ts`
* `apps/api/src/utils.ts`
* `apps/builder/src/build.ts`
* `apps/builder/src/git.ts`
* `apps/builder/src/index.ts`
* `apps/builder/src/postprocess.ts`
* `apps/builder/src/upload.ts`