Add category feature for reasons

[Ablebil]

You need to give 'em category, bruh.
Now you can say no professionally, personally, or just for the lolz.
Categories supported: professional, personal, funny, relationship, direct, and grateful.

[Fordi]

Have a look at #17, which I think should be merged. It shouldn't be hard to extend that idea categorically as well; e.g., reasons/en.json (default: professional), reasons/en_personal.json, etc. Fallback would be to professional when a given category is not available for a requested language. Separator is _, because country-specific languages are ln-CC, so that reduces ambiguity.