Add synthesis and translation-service documentation

[ajskateboarder]

These are a couple of small internal APIs, but I think they are worth documenting for reverse-engineering purposes :)

[ajskateboarder]

I also noticed that you've named the two similar-looking options and , do those actually accept different kinds of values?

It seems the \ parameter is for written languages (e.g. en, hi, ja) while the \ param is for spoken language (e.g. en-US, hi-IN, ja-JP). I'll reword them to be less ambiguous, maybe use locale and speech locale

[ajskateboarder]

@towerofnix Bump on the review 👀

I made changes based on what you have suggested

[ajskateboarder]

Thanks for your edits. They definitely added more clarity, lgtm ^^

[towerofnix]

Merged - thank you!