Skip build for docs-only changes

[code-asher]

It would be nice to not have to wait for a full build when submitting docs-only changes.

[code-asher]

Since we have required steps we would not be able to use conditional workflows unfortunately but we can do something like skip the build if nothing in src or lib changed.

[jsjoeio]

That would surely speed things up and improve our productivity. I think we should tackle this soon.