message: chore: Add line about updating documentation to PR template
diff: @@ -18,5 +18,6 @@ Before this pull request can be merged, a core maintainer will check whether
  - semver.major: Breaking changes. This includes changing interfaces or configuration behaviour.
  * [ ] the correct branch is targeted. Patch updates can target main, other changes should target the latest versions/* branch.
  * [ ] the RELEASE_NOTES.md document in case of relevant feature or config changes.
  + * [ ] any relevant documentation was updated to reflect the changes in this PR.
  <!-- Try to check these to the best of your abilities before opening the PR -->
  