docs: add notice to enable fork repo mirroring
requested to merge KevSlashNull/gitlab-vscode-extension:docs--add-notice-to-enable-fork-repo-mirroring into main
Overview
This MR adds a notice in CONTRIBUTING.md
that (new) contributors should set up pull mirroring to
- keep their fork up to date, and
- to avoid an out-of-date
main
to cause false negatives of the commit linting (until #288 is resolved).