Ship stylelint default config in package

[glenstaes]

In PR #15 we added support for linting stylesheets and generate a .stylelintrc file.

It would be nice that we could ship the PPW defaults inside the package so that the generated file would look like this:

{
  "extends": "@ppwcode/angular-schematics",
  "rules": {}
}

This would allow us to update the defaults as a new version of the package and all that needs to be done is give it an upgrade in a project.

Beneficial side-effect will also be that any rules that will be present in the .stylelintrc are only those rules deviating from our own defaults instead of the "default" defaults.