Add initial e2e testing with cypress

Add e2e tests with cypress using `vue add e2e-cypress`.

Vue CLI does not support creating typescript tests at this moment
(vuejs/vue-cli#1350).

.github/workflows/test.yaml

@@ -31,3 +31,7 @@ jobs:
       -
         name: Run integration tests
         run: npm run test:integration
+      -
+        name: Run e2e tests
+        if: always() # Run even if previous step fail
+        run: npm run test:e2e -- --headless