Feature Request: Add Boost block

### What

I've come to really enjoy the Reply block ; it allows me to participate in ongoing conversations from my WordPress site, and the bookmarklet makes that even easier.

I'd love to have something similar for another important part of my activity on the Fediverse: boosting / reposting posts. It would be nice if, using a bookmarklet, I could quickly create a new post that would include the necessary context to boost someone else's post (via a block, like the reply block).

### Why

Boosts / reposts are an important part of the Fediverse ; they allow folks who may not be otherwise very active to promote other conversations, and amplify other people's voices.

### How

_No response_