Update dependency typescript to v3.9.9

package.json

@@ -79,6 +79,6 @@
     "react": "17.0.2",
     "react-async": "10.0.0-alpha.0",
     "react-dom": "17.0.2",
-    "typescript": "3.8.3"
+    "typescript": "3.9.9"
   }
 }