ci: run the Playwright e2e suite alongside unit tests

The e2e suite already caught two real bugs this pass (hardcoded
inline canvas sizing, hidden output-actions staying visible) that
jsdom's unit tests structurally can't catch. Leaving it out of CI
would let the same class of bug back in unnoticed.

Author: ctkrug

.github/workflows/ci.yml

@@ -21,3 +21,5 @@ jobs:
       - run: npm run lint
       - run: npm test
       - run: npm run build
+      - run: npx playwright install --with-deps chromium
+      - run: npm run test:e2e