Add Text Alignment Support to the Pullquote Block

[porada]

Description

This PR adds support for specifying text alignment inside the Pullquote block using a block toolbar control.

Our users expect the center alignment option to be available (#22784, #31558, Automattic/wp-calypso#52519), because it used to also align the text inside the quote to center. That option was removed probably with the introduction of the Solid Color block style which aligned text to the side. This PR allows the user to overwrite the default alignment defined by any of the available block styles.

Behind the scenes, this PR also adds support for the placeholder attribute in the standard AlignmentToolbar control. This allows the control to reflect the currently used setting without explicitly setting the value.

How has this been tested?

• Pull the changes.
• npm run test-unit
• Open the editor.
• Insert an instance of the Pullquote block.
• Set the block style to Solid Color.
• Use the new toolbar control to overwrite the default text alignment.
• Make sure the custom text alignment option works intact with any other block alignment and block style option available—both in the editor and on the preview.

Screenshots

Types of changes

New feature

Checklist

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I’ve tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I’ve included developer documentation if appropriate.
• I’ve updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).

[porada]

Just making a note that the failing check keeps encountering a timeout. The suite should run just fine locally.

Also, please let me know if I should turn 8225d47 into a separate PR.

[yansern]

I am testing this on the latest rebased 10.7.1 version.

Unit tests are passing. (There was one failing test unrelated to this PR.)

Text alignment on pullquote block works as expected.

IMO the codes are clean & excellent.

[yansern]

Excellent CSS commenting style. 👍

[draganescu]

Plus one to that! 👏🏻

[porada]

I can the see the PR has diverged a bit from the trunk over time. Once there is a clear desire to merge this in, I’ll be happy to resolve all the conflicts. Just let me know.

[SiobhyB]

👋 @porada, I did some testing to double-check whether this change has any impact on the iOS and Android apps. I didn't run into issues, but there have been some updates to block settings in the apps in the last few months that aren't included in this PR (more specifically, the introduction of global styles). It'd be great to test again when the PR's updated from trunk, so that we can confirm that all the settings still work as expected on mobile.

Would you be able to give me a ping whenever this PR's updated? I'll follow along with this issue for any updates, too. Thanks!

[Mamaduka]

Hi, @porada

Can you rebase this branch on top of the current trunk?

Thanks

[carolinan]

Text align was added to the block in #30951.