Unit (+other) tests for the frontend

[sampsapenna]

Description

As the frontend is now created using Vue-CLI, it can be unit tested with ease.
The unit (and other if required) tests for the frontend should be written.

DoD (Definition of Done)

The frontend is adequately tested.

Testing

Running the newly written unit (+other) tests after they have been written.

[blankdots]

also introduce typescript