Allow init hosting:github to specify project

### The use case you're trying to solve

I have 2 firebase projects, live and test.
I just want PR's to deploy to the test server (or perhaps monitor a "test" branch and deploy when merged.

### Change to the action that would solve that use case

when using the nice `firebase init hosting:github` it creates a service worker who only has access to the live project (and it seems it is specifying this automatically)

I tried uising `-P test` on this command, and it seems to have ignored it, is this a bug?