chore: upgrade typedoc, add @types/node dependency

@types/node seems to now be necessary to access process.env

package.json

@@ -59,6 +59,7 @@
     "@types/chai": "^4.0.3",
     "@types/loglevel": "^1.4.29",
     "@types/mocha": "^5.2.6",
+    "@types/node": "^12.7.2",
     "chai": "^4.1.0",
     "clean-webpack-plugin": "^1.0.1",
     "cross-env": "^5.1.3",
@@ -87,7 +88,7 @@
     "ts-loader": "^4.1.0",
     "tslint": "^5.14.0",
     "tslint-loader": "^3.5.3",
-    "typedoc": "^0.14.2",
+    "typedoc": "^0.15.0",
     "typescript": "^2.6.1",
     "webpack": "^4.39.2",
     "webpack-cli": "^3.3.2",