Add more social media link icons

Problem/Motivation

For the Drupal.be I wanted to add links to our Facebook Group & Mastodon account at drupal.community.
These do not generate an icon, like Meetup, Linkedin, etc.. do.
I guess we can add them to our instance individually, but would be good to get that fixed upstream.

Maybe we need to make use of the new Icon API in Drupal? https://www.drupal.org/docs/develop/drupal-apis/icon-api →