Update dependency terser-webpack-plugin to v2.3.8

Author: renovate-bot

package-lock.json

@@ -50,7 +50,7 @@
     "size-plugin": "1.2.0",
     "stylelint": "10.1.0",
     "stylelint-config-standard": "20.0.0",
-    "terser-webpack-plugin": "2.3.4",
+    "terser-webpack-plugin": "2.3.8",
     "ts-loader": "6.2.1",
     "tslint": "^6.1.0",
     "tslint-clean-code": "0.2.10",