Publish on crates.io and docs.rs

[edwloef]

As the title states. clack-common, clack-extensions, clack-host and clack-plugin don't seem to be taken on crates.io and the library claims to be feature complete, so to me it would make sense to publish. Is there anything preventing this from being the case?

[haedrichowen]

I agree - @prokopyl thoughts? I would do this if you don't want to use the time