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Have you read the Contributing Guidelines on issues?

• I have read the Contributing Guidelines on issues.

Motivation

I realized there are a few text labels in our repo that are accidentally not translated. This has happened a few times in the past as well (see #4542). It would be interesti

There are a lot of images inside markdown that are either img tags or markdown images. Need to use next/image component instead of img tags and markdown images.

Edit: These changes are needed for beta.reactjs.org site

As brought up at p5T066-3c9-p2#comment-12233, it'd be nice to display the app's current locale as a secondary label to the main Interface Language label under App Settings:

This could likely be achieved by utilising `mLanguagePreference.setSumma