CI: run browser tests also on Linux

To test platform potential specific code of e.g. the WebCrypto API

Testing on Windows would be nice too, but all browsers fail to fetch resources
from the web-test-runner server.

.github/workflows/tests.yml

@@ -57,8 +57,15 @@ jobs:
 
   test-browsers-latest:
     name: Browsers (latest)
-    runs-on: ubuntu-latest
     needs: build
+    strategy:
+      fail-fast: false # if tests for one version fail, continue with the rest
+      matrix:
+        # run on all main platforms to test platform-specific code, if present
+        # (e.g. webkit's WebCrypto API implementation is different in macOS vs Linux)
+        # TODO: windows-latest fails to fetch resources from the wtr server; investigate if the problem is with path declaration or permissions
+        runner: ['ubuntu-latest', 'macos-latest']
+    runs-on: ${{ matrix.runner }}
 
     steps:
       - uses: actions/checkout@v4
@@ -79,17 +86,19 @@ jobs:
           npm pkg delete scripts.prepare
           npm ci
 
-      - name: Get Playwright version
+      - name: Get Playwright version and cache location
         id: playwright-version
         run: |
           PLAYWRIGHT_VERSION=$(npm ls playwright --depth=0 | grep playwright | sed 's/.*@//')
           echo "version=$PLAYWRIGHT_VERSION" >> $GITHUB_OUTPUT
+          PLAYWRIGHT_CACHE=${{ fromJSON('{"ubuntu-latest": "~/.cache/ms-playwright", "macos-latest": "~/Library/Caches/ms-playwright"}')[matrix.runner] }}
+          echo "playwright_cache=$PLAYWRIGHT_CACHE" >> $GITHUB_OUTPUT
       - name: Check for cached browsers
         id: cache-playwright-browsers
         uses: actions/cache@v4
         with:
-          path: ~/.cache/ms-playwright
-          key: playwright-browsers-${{ steps.playwright-version.outputs.version }}
+          path: ${{ steps.playwright-version.outputs.playwright_cache }}
+          key: playwright-browsers-${{ matrix.runner }}-${{ steps.playwright-version.outputs.version }}
       - name: Install browsers
         if: steps.cache-playwright-browsers.outputs.cache-hit != 'true'
         run: |