Add user feedback capability to the documentation

[huijing]

We are thinking about implementing https://www.feelback.dev/blog/new-astro-starlight-integration/ on the web monetization docs site as a trial to see if it is worth expanding to all our documentation sites.

[melissahenderson]

I think the Tagged Message Feelback would be the best option. Knowing whether a page was helpful isn't helpful to us if we don't know why. Tagged Message is the type that allows for a sentiment and a message.

Frankly, I like Stripe's messaging. It's straightforward: "Was this page helpful?" and clear: the Yes/No buttons are labeled as such and also have the thumbs up and thumbs down. I don't particularly like using hands in docs because some gestures that are positive in one culture can be negative in another. However, including yes/no makes the meaning clear.

We can work out the details for the feedback screens later.