Typescript: unknown compiler options should not stop parsing of tsconfig.json

[mhegazy]

If a tsconfig.json has an unknown option, the whole tsconfig.json is thrown away. This is too drastic. instead, only unknown properties should be ignored, and other properties kept.

[Arnavion]

But please warn about them to help catch typos.

[DanielRosenwasser]

--wranAbuotUknownOptionss

[basarat]

If a tsconfig.json has an unknown option

I think an valid compile output but with a error message + code (just like a type failure) would be nice :rose: