PLANET-4334 Allow a list of non-P4 urls not to have the :arrow_upper_right: icon

[oekeur]

Summary

Adds the option to define a list of "Commonly used domains" under "Social" settings. These domains should not get the external link icon and should always open in a new tab

As discussed in: https://github.com/greenpeace/planet4/issues/174

Testing

• Under "Social" > "Commonly used external domains" add https://www.google.com (or another variation of the url)
• Test with content:

<!-- wp:paragraph -->
<p><a href="https://www.google.com">External link marked as commonly used</a><br>
<a href="https://www.google.com/android/find">Link with path marked as commonly used</a><br>
<a href="https://www.planet4.test/privacy-and-cookies/" data-type="page" data-id="232">Internal link</a> <br>
<a href="https://www.youtube.com/">External link NOT marked as commonly used</a></p>
<!-- /wp:paragraph -->

(or of course with any other content)

[oekeur]

Ping :) @lithrel @mleray

[oekeur]

Hey @mleray ! Is this still relevant? :sweat_smile: I'll happily fix or close :)