Tutorial: Add custom social link services/icons

[bph]

Discussed in #380

^{Originally posted by justintadlock July 7, 2025}
Gutenberg 21.1 made it possible to create a Social Link block variation that supports alternative social services: WordPress/gutenberg#70261

We need a good step-by-step guide on how theme and plugin authors can use this. This is a quick, one-off tutorial, but it could be really fun!

[justintadlock]

Plugin here: https://github.com/wptrainingteam/devblog-custom-social-icons

Working on draft here: https://docs.google.com/document/d/1vajEHLZPYcoh8F0kUfH3eDr7I6lJb_DNsvFB-TwIvdA/edit?usp=sharing

[jonathanbossenger]

1st review done, left some suggestions on the article. Nice work!

[bph]

Also reviewed the article @justintadlock People will love this tutorial, I hope.