Add Blockquote to Comment Editor

[gmeben]

There is no blockquote option available on the comment editor. This is particularly odd considering that blockquotes are included by default when initiating quote replies to comments.

Add blockquotes as a selectable option to the comment editor.

Review Checklist

• Block quotes can be selected in comments
• Necessary frontend unit testing has been added
• Necessary integration testing has been added
• Documentation has been updated to reflect new changes

Accessibility Checklist

• Option can be selected with the keyboard
• No new color contrast issues are introduced
• Changed text has a font size of at least 16px
• Changed text uses plain language