Update dependency tslint to v5.20.1

Author: renovate-bot

src/package-lock.json

@@ -37,7 +37,7 @@
     "style-loader": "0.23.1",
     "terser-webpack-plugin": "^2.0.0",
     "ts-loader": "5.4.5",
-    "tslint": "5.15.0",
+    "tslint": "5.20.1",
     "typescript": "3.7.5",
     "url-loader": "1.1.2",
     "webpack": "4.29.6",