chore(meta): Add details to contrib doc about delete with redirect (#22630)

* chore(contrib): Add details of delete with redirect flag

* chore(contrib): Add details of delete with redirect flag

* chore(contrib): Add details of delete with redirect flag

* chore(contrib): Add warnings that documents must not be deletd without adding redirects

* Apply suggestions from code review

Co-authored-by: Hamish Willee <hamishwillee@gmail.com>

* Update CONTRIBUTING.md

* Apply suggestions from code review

Co-authored-by: Dipika Bhattacharya <dipika@foss-community.org>

* Update CONTRIBUTING.md

Co-authored-by: Dipika Bhattacharya <dipika@foss-community.org>

* chore(meta): Make markdownlint happy

Co-authored-by: Hamish Willee <hamishwillee@gmail.com>
Co-authored-by: Dipika Bhattacharya <dipika@foss-community.org>