Run Cypress tests on Safari and Firefox

### Description

Currently our Cypress tests are only run on Chrome. To ensure apps work in other browsers, we should run tests on the most common browsers, Chrome, Firefox and Safari.

We recently had an incident where apps were broken on Safari browsers: https://github.com/Altinn/app-frontend-react/issues/312

### Additional Information

Cypress doesnt actually have support for Safari yet ([current supported browsers](https://docs.cypress.io/guides/guides/launching-browsers#Browsers), [github issue for Safari support](https://github.com/cypress-io/cypress/issues/6422)), so we need to figure out a way to work around this.
Some options:
- Write some smoke tests in a different framework for Safari
- Investigate if there are some adapters that can be used to run tests written in cypress on another framework (perhaps https://github.com/vladlearns/cypress-playwright can be used?)

### Tasks

_No response_

### Acceptance Criterias

- [ ] End2End tests are run on Safari as part of Github workflow
- [ ] End2End tests are run on Chrome as part of Github workflow
- [ ] End2End tests are run on Firefox as part of Github workflow

Start by reviewing the existing Cypress setup and GitHub workflow to see how Chrome end-to-end tests are currently launched. Investigate a viable way to run the tests on Firefox and Safari, noting Cypress's stated lack of Safari support; done means the workflow runs end-to-end tests on Safari, Chrome, and Firefox.

Written by the indexing model from the issue text.