This way MkDocs will be able to report errors for broken links

Done with:

perl -0777 -i -pe \
's@(?<!!)\[([^\]]*)\]\((?!https?://)(?!mailto:)(/(?:(?:(?:/(?![\)#]))|[^/)#])(?!.md))+)/?(#[^)]*)?\)@[$1]($2.md$3)@gm' \
`find . -name '*.md'`

Migrated from the following two sources

https://github.com/civicrm/civicrm-buildkit/blob/d20229ac9f63aaf183687157a5e655c953b81f5e/doc/daily-coding.md#housekeeping
https://civicrm.stackexchange.com/questions/17717/how-do-i-upgrade-civicrm-on-a-local-site-that-i-installed-with-buildkit-civibuil/17721#17721

Not adding internal redirects because these pages are so new.

Based on discussion here:
https://github.com/civicrm/civicrm-dev-docs/pull/189