Extend Twitodon to revoke Mastodon token after use

[ineffyble]

As per the docs you should be able to call the "Revoke token" endpoint to revoke the token, similar to what's currently done for Twitter.

[lucyllewy]

AFAICT that endpoint only revokes the current session - it doesn't disassociate the app from your account. The revoke feature in use for Twitter actually revokes all access from the app, not just the current session. I had to add the revoke feature for Twitter because Twitter's own user-interface prevents removing the app from your account entirely - it's a workaround for their broken feature, for which there is no Mastodon equivalent.