Documentation: Explain how to translate Gutenberg in standalone apps using the editor packages

[youknowriad]

Related #53874

What?

This PR add a small documentation page about the i18n of the @WordPress packages. It explains how to load translations and how to switch to RTL if needed. I think there's a missing part about the localization (@wordpress/date package).

I also think that it would be good to explain here how to generate the list of all strings from the packages. (or provide translations and strings for some languages). I'm not sure whether it's possible to just provide the WordPress ones here from GlotPress, maybe there's a way/link to download them and use them manually.

Anyway, I think the current docs should be fine for a start.

Note I have personally tested all the code examples in a third-party vite install.

Test the documentation website

cd platform-docs
npm install
npm start

[priethor]

Thanks, Riad! LGTM.

I added a small suggestion, but it is not a blocker at all.

[tyxla]

Looks good, suggesting a fix for a minor typo.

As for expanding, I think we could borrow a bit from the respective READMEs of the i18n and date packages.

[github-actions]

Flaky tests detected in d100a2c.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/6420255033
📝 Reported issues:

• [Flaky Test] should partially select with shift + click (@webkit) #53524 in /test/e2e/specs/editor/various/multi-block-selection.spec.js