Closes https://codeberg.org/forgejo/forgejo/issues/6093
This PR adds support for **multi-line review comments** on pull requests, allowing reviewers to select a range of lines in diffs instead of only a single line — similar to GitHub's implementation.
### Tests for Go changes
- I added test coverage for Go changes...
- [X] in their respective `*_test.go` for unit tests.
- [X] `make pr-go` before pushing
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/12582
Reviewed-by: Mathieu Fenniak <mfenniak@noreply.codeberg.org>