[CI] Run basic markdown-file checks when a PR is submitted

[chalin]

• Set up checks via NPM packages and scripts - Basic tooling: link & spell check, and formatting #231
• Set up GH actions to trigger on PR submission - [CI] Run checks over PRs #235

[chalin]

@nate-double-u - I don't seem to have the permissions to fully implement the tasks in this PR. Could my access permissions be bumped, if only for the period necessary to implement CI?

[nate-double-u]

I think we can bump your permissions, we'll have to update cncf/people repo.

[nate-double-u]

Once approved, cncf/people#464, will provide you Admin access to cncf/techdocs, @chalin.

[chalin]

Thanks @nate-double-u!