Suggestion: Enforce using `deno fmt`

[ClaudiuCeia]

Hi team,

I sent a small PR today and noticed that formatting is not enforced in any way. Out of habit I ran deno fmt only to see quite a few unrelated changes that I had to manually revert.

I think it would improve dev experience if contributors were expected to use deno fmt when submitting patches (or have this setup as a GitHub action)