[CODEOWNERS] need an entry for sdk/translation/ai-translation-document-rest

[jeremymeng]

Currently it falls back to js-dev team.

/cc @ronniegeraghty do we have a proper label?

[ronniegeraghty]

@jeremymeng does Document Translation get it's only library? Looking at service docs it appears to be a feature of the AI Translator Service.

[jeremymeng]

@ronniegeraghty I am only seeing Cognitive - Translator in this repo. Should we use that one for this?

[ronniegeraghty]

That's what I would go with for now. Until the service team tells us it's a standalone service or they need different labels for more detailed tracking.

[jeremymeng]

Sounds good!