Merge branch 'docs-kenneth-project-group-redirects' into 'master'

Add documentation for new project/group redirects

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/167723



Merged-by: Lorena Ciutacu <lciutacu@gitlab.com>
Approved-by: Lorena Ciutacu <lciutacu@gitlab.com>
Reviewed-by: Lorena Ciutacu <lciutacu@gitlab.com>
Co-authored-by: Kenneth Chu <ksiuhengchu@gitlab.com>