docs: add `after first line` to the list of collected keys

[muzimuzhi]

Commit 3cb41f7 (2.5.0, 2023-10-16) solved the code part of #28, and this PR adds the missing documentation part.

The new key is inserted assuming the whole list is currently in lexicographic order.

Feel free to adjust the wording and classification of changelog entry before merging. With "Allow edits by maintainers" checked (by myself, the PR author), users with write access to this repo can add new commits to my docs/collect-data branch. You can use git fetch origin pull/<pr-id>/head:<local-branch-name> to checkout my fork's docs/collect-data locally, and modify and push it as normal. (gh pr checkout <pr-id> may fail on a shallow clone, see https://github.com/cli/cli/issues/4287.)

Related GitHub Docs articles

• "Checking out pull requests locally"
• "Committing changes to a pull request branch created from a fork".

[T-F-S]

Oops, I forgot this documentation. Thank you for correcting this.

Technically, I will close this pull request, but I copied the necessary lines manually and added them to my source.