Add is_rtl flag to supportedLanguages for RTL support (#51187)

[UncoveredBread]

Implements AIRFLOW-51187 by adding is_rtl flag to supportedLanguages in config.ts to support RTL languages like Hebrew. Language switcher not available in UI (depends on #51038), but flag is implemented. Most frontend tests passed; some unrelated failures due to test setup issues.
Fixes #51187.

[boring-cyborg]

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[bbovenzi]

I would prefer we use a real boolean value of true or false instead of yes or no strings

[pierrejeambrun]

+1

[eladkal]

The goal of #51187 is also to implement the RTL support

[jscheffl]

The goal of #51187 is also to implement the RTL support

So this PR would "just" add the flag wO7 any functionality behind? Or is it WIP and the RTL logic will be pushed in a moment? I am asking because if the logic would come in a separate PR I'd favor to add the needed flags there.

[eladkal]

I am asking because if the logic would come in a separate PR I'd favor to add the needed flags there.

The logic to support RTL should be in this PR

[guan404ming]

You could reference this doc to implement! Feel free to ask question if there is anything I could help.

[guan404ming]

For not blocking rtl langs' translation for too long, I open another pr for handling the logic part #51376.

[pierrejeambrun]

Closing in favor of:
#51376