fix(angular): Fix --multi-app support for ng-add schematic

[SchnWalter]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Ionic CLI added a new "--multi-app" option for working with mono-repositories in ionic-team/ionic-cli@42c5199, this includes improved support for updating Angular CLI workspaces by using

ng add @ionic/angular --project=demo-project

This behavior is documented in the new Angular-Monorepo wiki page; but the generated angular.json file is not valid because some schematic code always uses app as the project name.

To reproduce the issue, just follow the steps described in the Angular-Monorepo wiki page, but don't use app as the default project name, use mobile or whatever you prefer.

This MR is related to one of the issues for which the new flag was introduced: ionic-team/ionic-cli#4192

What is the new behavior?

The --project=... argument is now respected by the ng add schematic.

Does this introduce a breaking change?

• Yes
• No

cc: @dwieeb