WIP: ci: run Playwright-based UI tests

The UI tests are most beneficial when they are run regularly ;-)

To this end, let's run them on every PR, and let's allow running it
manually with the deployed website.

Signed-off-by: Johannes Schindelin <[email protected]>

.github/workflows/playwright.yml

@@ -0,0 +1,22 @@
+name: Playwright Tests
+on:
+  pull_request:
+  workflow_dispatch:
+jobs:
+  test:
+    timeout-minutes: 60
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - uses: actions/setup-node@v4
+      with:
+        node-version: lts/*
+    - name: Install Playwright Browsers
+      run: npx playwright install --with-deps
+    - name: Run Playwright tests
+      run: npx playwright test
+    - uses: actions/upload-artifact@v4
+      if: always()
+      with:
+        name: playwright-report
+        path: playwright-report/