fix: add type defs for react

Author: deankevorkian

package.json

@@ -49,7 +49,9 @@
     "rollup-plugin-atomic": "^2.0.1",
     "shx": "^0.3.3",
     "tslib": "^2.1.0",
-    "typescript": "^4.1.3"
+    "typescript": "^4.1.3",
+    "@types/react": "^17.0.1",
+    "@types/react-dom": "^17.0.0"
   },
   "atomTestRunner": "./spec/runner",
   "activationHooks": [