Add writing-mode as a typography block support

[poena]

This ticket is for tracking the PHP backport for the following Gutenberg PR:
​https://github.com/WordPress/gutenberg/pull/50822

[poena]

Add writing-mode typography block support

Trac ticket: https://core.trac.wordpress.org/ticket/59306

Just doing a quick PR from the patch on the ticket to run CI on it (and also because I find the GH diff easier to read 😄)

[isabel_brison]

Changes LGTM; there was a linting error which I fixed in the attached PR: ​https://github.com/WordPress/wordpress-develop/pull/5210

I was wondering if we should add a test for this feature in the typography test suite: ​https://github.com/WordPress/wordpress-develop/blob/trunk/tests/phpunit/tests/block-supports/typography.php but we're not being consistent with tests for other discreet features such as letter-spacing or text-decoration so I guess we could leave this as is and revisit those tests later as a whole.

[isabel_brison]

In 56605:

Editor: add text orientation for blocks with typography support.

Adds a new text orientation option to the typography block support, implemented with CSS writing-mode.

Props poena.
Fixes #59306.

committed in r56605.