test(angular): add Angular app for testing

[christian-bromann]

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 for affected output targets
• Tests (npm test) were run locally and passed
• Prettier (npm run prettier) was run locally and passed

Pull request type

This patch adds an Angular app for testing the generated output target.

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): testing

What is the current behavior?

We don't really test how the Angular output target behaves when integrated in a real Angular app. This patch adds an guinea pig app that allows us to do it.

Does this introduce a breaking change?

• Yes
• No

Other information