chore(package): update @types/react-dom to version 16.9.7

Closes #36

Author: greenkeeper[bot]

package.json

@@ -15,7 +15,7 @@
   "devDependencies": {
     "@types/chrome": "0.0.93",
     "@types/react": "16.9.16",
-    "@types/react-dom": "16.9.4",
+    "@types/react-dom": "16.9.7",
     "css-loader": "3.3.0",
     "eslint": "6.8.0",
     "prettier": "2.0.0",