[ Feat ] Validate whisky.json

[gpibarra]

I was modifying the whisky.json file and by mistake generated an invalid json file (a trailing comma).
When running whisky update, the error was not clear enough, because doing json_decode() did not check if the file was well formed and returned null
From there, I decided to also implement the validation of all json properties to avoid future errors.

PS: need to do the build.

[ProjektGopher]

This looks super promising! I'm excited to look through it properly when I'm sitting at a computer after I get my kid down for the night