Google’s multi-language input method, known as Google Input Tools is a good example of a web app that uses transliteration to input non-English characters. The basic idea is to have a text box, in which users spell the words of their own language, using English characters. They usually type those words using an English keyboard. The web app converts the typed English keystrokes into characters of their local (non-English) language, and displays those non-English characters in the text box in real-time.

https://www.smashingmagazine.com/2020/03/keyboard-event-related-bugs-browser-based-transliteration/