install latest playwright on test

Author: keithamus

package.json

@@ -15,7 +15,7 @@
     "bundle": "esbuild --bundle dist/index.js --keep-names --outfile=dist/bundle.js --format=esm",
     "build": "tsc && npm run bundle && npm run manifest",
     "prepublishOnly": "npm run build",
-    "pretest": "npm run build",
+    "pretest": "npm run build; npx playwright install",
     "test": "web-test-runner",
     "postpublish": "npm publish --ignore-scripts --@github:registry='https://npm.pkg.github.com'",
     "manifest": "custom-elements-manifest analyze"