Run E2E tests on different viewports

[ivarnakken]

Cypress gives us the ability to specify its viewport, and it also includes predefined values such as for iphone-5. This can be utilized to test mobile view, which often seem to be forgotten when developing. Since running everything twice would be costly, I imagine only doing it on the router spec is best, at least for now.

[eikhr]

Cypress has pretty good support for running things in parallell, it might be worth looking into to avoid increased CI pipeline time.