Social: Document guidelines and extensibility (#70961)

Co-authored-by: Mamaduka <[email protected]>
Co-authored-by: bph <[email protected]>
Co-authored-by: priethor <[email protected]>

Author: 3 people

packages/block-library/src/social-link/README.md

@@ -0,0 +1,21 @@
+# Social Icon block
+
+The Social Icon is a foundational block that displays various icons linking to different social profiles or sites. Each social service is registered as a variation of this block.
+
+
+## Adding new social icons
+
+The core maintains certain standards for adding new social icons. To add a new variation to WordPress, it must be well-established and popular.
+
+To evaluate if a social service should be added, contributors will consider the following factors:
+
+* Is the service popular enough for core developers to have heard of it before? Is it "mainstream?"
+* How long has the service been online?
+* Does it have a Wikipedia article?
+* Is there a plugin adding social icons in the repository that includes the services in question and has a considerable number of active installations?
+* Is this social service frequently requested?
+
+
+## Adding custom social icons
+
+Starting from WordPress 6.9, it's possible to add custom social icons to your site. See: [#70261](https://github.com/WordPress/gutenberg/pull/70261).