Although 'przenośność danych' (or in this case 'przenośne dane') is more accurate word-to-word translation of 'data portability', 'mobilność danych' is more accurate semantically and easier to understand
- add index.html into /lang/pl/ directory
- add polish language with 🇵🇱 flag into config.js so that new langueag can be fetched via /js/languagePicker.js
NOTE: Polish language is tricky with semantic and contextual meaning, so the translation may be reverified