chore: bump typedoc from 0.20.18 to 0.20.20 (#168)

Author: dependabot[bot]

package-lock.json

@@ -115,7 +115,7 @@
     "ts-jest": "^26.4.4",
     "tslint": "^6.1.3",
     "tslint-config-prettier": "^1.18.0",
-    "typedoc": "^0.20.18",
+    "typedoc": "^0.20.20",
     "typescript": "^4.0.5"
   },
   "dependencies": {