Load LTR and RTL stylesheets conditionally

[sejas]

Related issues

• Fixes STU-352
• Fixes STU-351

Proposed Changes

• Add a new component
• Load @wordpress/components css conditionally based on RTL and LTR.
• Load index.css a.k.a main_window.css after loading the WordPress stylesheet

Testing Instructions

• Run npm start
• Click on Help > what's new , to open the modal
• Observe the modal looks correct
• Change the language to any RTL
• Click on يساعد > what's new , to open the modal
• Observe the next back buttons are displayed inverted
• Observe the close buttons have the correct marging
• Make a general pass in the UI and observe everything looks correct in RTL languages

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• Run npm run make
• Open the app produced on out/Studio-darwin-arm64/Studio.app
• Observe the styles work as expected.

https://github.com/user-attachments/assets/e50e0675-b32f-43b9-b04d-f6588399ca73

Before	After

Pre-merge Checklist

• [ ] Have you checked for TypeScript, React or other console errors?