Add a way for users to give us feedback on whether docs are good/useful

[chasenlehara]

It might help us know if docs are bad or broken if users have a way to provide feedback on each page.

This could be a star rating (taken from Google Analytics):

Or a 👍 👎 (taken from Apple support):

…or something else entirely. We’d need to figure out exactly how much info we wanted to collect and some UIs for doing this.

[nlundquist]

I think this is an excellent idea and should be a major element of #4116 rather than just a stretch goal. IMO even basic metrics like the thumbs up / down would be a great help to focusing our ongoing doc improvement efforts.

I can think of some ways we could implement this without a great deal of difficulty (a day or two of effort). I'll do this during the retreat if I get the chance.