build: update typescript compiler

Author: mgechev

package-lock.json

@@ -88,7 +88,7 @@
     "standard-version": "7.1.0",
     "ts-node": "8.5.4",
     "tslint": "5.20.0",
-    "typescript": "3.8.2",
+    "typescript": "3.9.6",
     "zone.js": "0.10.2"
   },
   "peerDependencies": {