Update dependency terser-webpack-plugin to v3.0.8

Author: renovate-bot

package.json

@@ -130,7 +130,7 @@
     "webpack-cli": "3.3.12",
     "webpack-dev-server": "3.11.0",
     "optimize-css-assets-webpack-plugin": "5.0.3",
-    "terser-webpack-plugin": "3.0.7",
+    "terser-webpack-plugin": "3.0.8",
     "webpack-merge": "4.2.2"
   }
 }