feat: add arabic readme

[zodplugin]

Added an Arabic translation of the README (README_ar.md) to make the project more accessible to Arabic-speaking users.

[pszymkowiak]

Thanks for the Arabic translation! A few things needed before we can merge:

1. Add language link to all existing READMEs — each README has a language selector at the top. Please add the Arabic link to all of them (README.md, README_fr.md, README_zh.md, README_ja.md, README_ko.md, README_es.md). See PR feat(docs): add Indonesian README translation #399 or Added German Translation  #456 for the pattern.

2. Rebase on develop:

   git fetch upstream develop
   git rebase upstream/develop

3. Add DCO sign-off:

   git commit --amend -s --no-edit
   git push --force-with-lease