Documentation only changes shouldn't require a CI loop build

[jonthysell]

I just submitted a PR #3641

It only has doc changes, and I specifically picked none when using yarn change.

And yet, it's building everything.

[chrisglein]

This PR shouldn't have actually needed to. It's the fact that you had a changefile that made it a requirement. MD files should be exempt. So... for this kind of change don't preemptively make a changefile?