New port: irc/bitlbee-mastodon: Bitlbee plugin to communicate with Mastodon instances

This plugin allows Bitlbee to communicate with Mastodon instances. Mastodon
is a free, open-source, decentralized microblogging network. Bitlbee is an
IRC server connecting to various other text messaging services. You run
Bitlbee and connect to it using an IRC client, then configure Bitlbee to
connect to other services, such as a Mastodon instance where you already
have an account. The benefit is that you can now use any IRC client you
want to connect to Mastodon.

WWW: https://alexschroeder.ch/software/Bitlbee_Mastodon

PR: 235731
Submitted by: tobias.rehbein@web.de
Reviewed by: mat
Approved by: mat (mentor)
Differential Revision: https://reviews.freebsd.org/D19205