chore(deps): update dependency typedoc to ^0.20.0

Author: renovate-bot

package.json

@@ -44,7 +44,7 @@
     "tslint": "^5.12.0",
     "tslint-config-prettier": "^1.17.0",
     "typescript": "^3.2.4",
-    "typedoc": "^0.15.0",
+    "typedoc": "^0.20.0",
     "ts-jest": "^24.0.2",
     "jest": "^24.8.0",
     "jest-extended": "^0.11.2",