Add the ability to automatically switch the tts language for documents, whose content is tagged with the "lang" tag

[DraganRatkovich]

It would be nice to add a feature for certain types of html documents where the "lang" tag is used to indicate the language of the document or the languages in which the content is written, and enable automatic tts voice switching according to the language tag used.

This is useful, when the user wants to read a document that contains multiple languages and the user needs to use a different TTS voice for each language.