CI: setup HTTPS in web-test-runner for BrowserStack tests

To have tests work Browserstack Safari (also below iOS 15), as the tests are run in an iframe,
rewriting localhost as hostname, making WebCrypto not available.

We keep HTTP for the non-browserstack tests so that in local testing,
generating self-signed certs is not required.

.github/workflows/tests.yml

@@ -100,12 +100,12 @@ jobs:
         run: npx playwright install --with-deps webkit
 
       - name: Run browser tests
-        run: npm run test-browser -- --static-logging
+        run: npm run test-browser:ci -- --static-logging
 
       - name: Run browser tests (lightweight) # overwrite test/lib
         run: |
           npm run build-test --lightweight
-          npm run test-browser -- --static-logging
+          npm run test-browser:ci -- --static-logging
 
   test-browsers-compatibility:
     name: Browsers (older, on Browserstack)
@@ -119,6 +119,15 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
 
+      - name: Generate self-signed HTTPS certificates for web-test-runner server
+        uses: kofemann/action-create-certificate@v0.0.4
+        with:
+          hostcert: '127.0.0.1.pem'
+          hostkey:  '127.0.0.1-key.pem'
+          cachain:  'ca-chain.pem'
+      - name: Adjust HTTPS certificates permissions
+        run: sudo chown runner:docker *.pem
+
       - name: Install dependencies
         run: npm ci --ignore-scripts