Upgrade typedoc.

Author: brendanburns

package-lock.json

@@ -96,7 +96,7 @@
     "ts-mockito": "^2.3.1",
     "ts-node": "^8.2.0",
     "tslint": "^5.17.0",
-    "typedoc": "^0.19.2",
+    "typedoc": "^0.20.25",
     "typescript": "^4.1.3"
   },
   "bugs": {