Paragraph Block: Add Support for Underlining Text on WPCOM

[mdrockwell]

Is your feature request related to a problem? Please describe.
There is no built-in option for underlining text within the editor. It can be accomplished on iOS using the system's built-in options, but can't be done at all on Android.

[From @hypest] Scoped down the ticket to only be on WPCOM (see Matt Chowning's comment below)

Describe the solution you'd like
An additional button should be added above the keyboard when editing a Paragraph block that allows you to underline the highlighted text.

Additional context

From an app review:

Need underlined option for post.

[mchowning]

This is a bit of a spicy topic. 🙂

There's been discussion around this in #562. My understanding from that thread and my brief testing is that underlining is not permitted in Gutenberg core, but wp.com has changes that permit it, and to this point we've decided to not deviate from Gutenberg core. Do you think it would be worth adding a comment to that issue and closing this one @mdrockwell ?

[hypest]

May I suggest re-purposing this ticket to be WPCOM only? We can rename the title and we'd add that to the backlog.

[erricgunawan]

A question from 4767399-zen (translated):

How do I write underlining a word?

[hypest]

👋 @erricgunawan!

There is currently no UI support for toggling the underline format on text. The only way to currently do it is by switching to HTML mode (via the top level 3-dot menu) and type <span style="text-decoration: underline;"> before the text to underline, following by </span> to close the html tag.

[erricgunawan]

Oh, that's a good tip/workaround!

Thanks for letting me know @hypest!

[mdrockwell]

From an Android app review:

Cannot underline text.

[igotdes]

+1 from #5578989-zen:

And while you’re at it, can you add an underline text functionality to the WordPress iOS app in the block editor. It used to be there in the classic editor on the iOS app and it’s in the block editor on my laptop, but not in the WordPress iOS mobile app. You’ve got strikethrough, but how often does someone use strikethrough text versus underline text?

And for future reference as this took me a while 😅 in iOS, users can underline text by long-pressing on it to select, then clicking on Format > Underline.