update language name from 'বাংলা' to 'Bangla' for consistency

This PR improves the language list in langs.json and the README file. Changes: 1. Standardized Name: Updated "বাংলা" to "Bangla" to match international and official Bangladesh government standards. 2. Alphabetical Reordering: Moved the Bangla entry to its correct alphabetical position (after Afrikaans and before Bosnian) for better organization. 3. Consistency: All language names are now consistently displayed in English across the list.