chore: add element-internals-polyfill for tests

Author: asyncliz

package-lock.json

@@ -67,6 +67,7 @@
     "@types/jasmine": "^4.0.3",
     "@web/test-runner": "^0.18.2",
     "@web/test-runner-playwright": "^0.9.0",
+    "element-internals-polyfill": "^1.3.12",
     "jasmine": "^4.5.0",
     "rollup": "^2.79.1",
     "sass": "^1.52.3",