@Gargron link communities together.

Just like you can link to a user's profile with @, link to a topic with #, there should be a way to link to communities.

Imagine I'm looking for a community for artists and I ask my in my local timeline. A user then responds "Check out &mastodon.art"

The & symbol makes "&mastodon.art" into a hyperlink, when clicked it opens, not the website, but mastodon.art's local timeline. I can then interact with mastodon.art members in a non-local timeline.