Update dependency tslint to v5.20.1

Author: renovate[bot]

package.json

@@ -82,7 +82,7 @@
     "ts-loader": "^4.1.0",
     "ts-node": "^4.1.0",
     "tsconfig-paths": "^3.1.1",
-    "tslint": "5.3.2",
+    "tslint": "5.20.1",
     "webpack": "^4.2.0",
     "webpack-cli": "^2.0.13",
     "webpack-node-externals": "^1.6.0"