Comments: add a visual editor for comments

We received the following feedback internally.

I went to write a reply from the app and I was surprised I couldn’t include a link in there. I had to write the HTML manually. Also, when I did that, the keyboard added smart quotes for the href which I had to replace manually.

Adding a new comment (full-screen)	To edit on an existing comment	Editing an existing comment

Video: 1m41s
^{Tested with WPAndroid 15.8-rc-1 on Pixel 3 Android 11.}

Extra Notes

The subset of HTML tags which are allowed in comments are stored in the $allowedtags global variable. See https://core.trac.wordpress.org/browser/tags/5.5.1/src/wp-includes/kses.php#L414

We don't have a visual editor for comments on the web yet, but there is a tag inserter in the WP Admin > Comments section.

You can interact with comments in a few different locations: on rendered blog posts in a browser, Reader, Notifications, and in My Site > Comments or WP Admin > Comments. At the time of this writing, the only place I could find a tag inserter for comments in a default install was in WP Admin > Comments.

Automattic P2s have been using a modified plugin to use the Gutenberg block editor comments on a subset of P2s.
^{(internal reference: pb6Nl-do2-p2)}

ht @koke p4a5px-2CS-p2 https://github.com/wordpress-mobile/WordPress-iOS/issues/14973

Start by reviewing the comment entry points described in the issue: rendered blog posts, Reader, Notifications, and My Site > Comments. Compare the Android screenshots and the allowed HTML tags in WordPress's kses.php. Done means comments can be created and edited with a visual editor while preserving the permitted comment markup across the relevant Android flows.