Follow OS conventions for storing cache

[Arian04]

Hi, currently, .electron-gyp is stored in the home directory. I think it would be much nicer if the default could be changed so that it is stored in the expected cache directory for the OS as node-gyp did here.

I skimmed through the codebase and I think the only thing that would have to be done is to change this line to use env-paths to get the system cache directory (as node-gyp did in the referenced commit) and add it to the package.json.

I'm not familiar with typescript or this codebase, so I may be missing something. If I have time I might create a pull request for this.