[json] validation doesn't work offline

[drgullin]

• VSCode Version: 1.5.1
• OS Version: OS X El Capitan 10.11.3

Every time I launch VS Code when I'm offline, I get this error:

JSON validation doesn't work as a result.
I hope a schema reference can be initially cached inside the editor and downloaded once again when internet is on.

Steps to Reproduce:

1. Go offline (switch off the internet)
2. Open VS Code.
3. Open some json file
4. Work without validation but with an error.

[Arlen22]

I don't want it to use the cached file if I'm online, but it would be nice to cache files somewhere.

[MuTsunTsai]

I would love to have this feature as well. Caching JSON schemas will certainly improve offline user experience.