Add Bangla (bn) Localization Support

[Md-Sifatullah617]

💡 Motivation and Context

The feedback package did not support Bangla, which is needed for apps like Charge.AI serving Bangladeshi users.

💚 How did you test it?

• Manually tested in a demo Flutter app using BetterFeedback widget.
• Switched device/app locale to bn and verified translated text.

📝 Checklist

• I reviewed submitted code
• I added tests to verify changes (manual for now)
• I updated the docs if needed (README.md for new locale mention)
• All tests passing (if applicable)
• No breaking changes

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🔮 Next steps

• Consider adding support for other RTL languages like Urdu.
• Improve UI adaptability for translated text with longer phrases.

[ueman]

@Saad29 Can you help me on this, please? :)

[ueman]

@Md-Sifatullah617 Thanks for your contribution! Can you revert all changes that are unrelated to the translations? Otherwise, this already looks good to me. Obviously, I can't really tell whether the translations are good or correct since I don't speak the language. I hope that @Saad29 may be able to help with reviewing them, but if not, I'm going to merge it sometime later this week.

[Saad29]

@Md-Sifatullah617 Thanks for your contribution! Can you revert all changes that are unrelated to the translations? Otherwise, this already looks good to me. Obviously, I can't really tell whether the translations are good or correct since I don't speak the language. I hope that @Saad29 may be able to help with reviewing them, but if not, I'm going to merge it sometime later this week.

Heyy Jonas, sure thing !

[Saad29]

Translations look cool!

[ueman]

Thank you very much!

[Md-Sifatullah617]

Thank you @ueman and @Saad29 for your helpful feedback and support! 🙏
I've created a new, clean PR (#365) that includes only the translation-related changes as requested.
Closing this one in favor of that — please have a look when convenient.
Really appreciate your time and guidance throughout the process! 😊