Add Arabic (ar-AR) translation

[safsafa-dev]

Hi NocoBase team!

I noticed that Arabic translation is not available on the docs site.
Arabic is spoken by 400+ million people and could greatly expand
NocoBase's reach in the Middle East and North Africa region.

I'd like to contribute by:

• Adding Arabic (ar-AR) translation to the docs repo
• Translating the README to Arabic
• Starting with the most important pages first

Would you accept this contribution? I'm ready to start!