feat(): add mocks and testing module

[wbhob]

Summary of changes:

Intended/example use case:

Checklist:

• [ ] npm run build runs without error
• [ ] ng serve spawns app, Intercom messenger is visible and interactive, and there are no errors in the console

Closes issue: #57

Scott: here's my implementation of the mock version. I'd appreciate your review and maybe some help getting it as a secondary entry point.

Thanks!

[marc-wilson]

I think another check should be added here:

• [ ] ng test runs without any failure