fixes ngAdd schematic: options.project was always undefined

[JohannesHoppe]

Hello, gentlemen,

I'm pretty sure that the signature of the ngAdd schematic was broken. The affected code was directly copied from ngx-gh, so later on we might want to double-check that nobody else copied that error, too. In the end the value of options.project was always undefined. This was reported in #5.

BEFORE:

export const ngAdd = ({ project: DeployOptions }) => (
  tree: Tree,
  options: NgAddOptions
)

AFTER

export const ngAdd = (options: NgAddOptions) => (
  tree: Tree,
  _context: SchematicContext
)

I also didn't understand the original test:
https://github.com/mgechev/ngx-gh/blob/5088488a50af7550eb6b5b0dfcfac4ade6a61085/ng-add.spec.ts#L36-L47

Why should one installation override the next one in case of multiple projects? In the current implementation, both simply changes remain.
@mgechev could you please review this and tell me if I'm on the right track?

FYI @dianjuar

[mgechev]

LGTM

[JohannesHoppe]

👍