ci: run the Playwright tests on every deployment

Whenever deploying the site, it is a good idea to run the tests
afterwards.

An alternative would be to run the tests before deploying, but there are
challenges that would make this cumbersome:

- For deployments, we run Hugo with a specific base URL, which could let
  the UI tests redirect to the site that we want to deploy to, and
  therefore fail to verify the locally-built site.

- Even if an outside change (such as a change from the ProGit book
  repository) would break those tests, we would still want to deploy the
  site. This is better than falling behind just because no volunteer
  finds time to fix the issues.

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

Author: dscho

.github/actions/deploy-to-github-pages/action.yml

@@ -144,3 +144,17 @@ runs:
               await github.rest.issues.update({ ...req, state: 'closed' })
             }
           }
+
+    - name: Install @playwright/test
+      shell: bash
+      run: npm install @playwright/test
+    - name: Run Playwright tests
+      shell: bash
+      env:
+        PLAYWRIGHT_TEST_URL: ${{ steps.pages.outputs.base_url }}
+      run: npx playwright test --project=chrome
+    - uses: actions/upload-artifact@v4
+      if: always()
+      with:
+        name: playwright-report
+        path: playwright-report/