Add testing for client-support-angular

[ndricimrr]

Currently our client-support-angular package is missing tests.

Aim of the tests should be to check:
1 - That the package does not break when switching/working with different Angular versions: v11, v12, v13
2 - The intended functionality works as expected.

Investigate Task (1) and (2) and derive next steps. Task can be split in subtasks.

Potential related follow-up: #2112

[wdoberschuetz]

Here's what I think is a good way to divide this task into the following:

1. Creating/updating a Travis so that it runs client-framework-support tests
2. Writing unit tests where it makes sense for the client-framework-support services/components
3. Writing integration tests that test importing of the lib and using its functions (i.e. Implement tests by using LuigiMockModule #2112)
4. Expand Travis to include testing for three latest Angular versions