ci: Update terser-webpack-plugin (#936)

package.json

@@ -90,7 +90,7 @@
     "stylelint-config-recommended": "^2.2.0",
     "stylus": "^0.54.5",
     "stylus-loader": "^3.0.2",
-    "terser-webpack-plugin": "^1.4.1",
+    "terser-webpack-plugin": "^2.1.0",
     "webpack": "^4.35.2",
     "webpack-cli": "^3.3.5",
     "webpack-dev-server": "^3.7.2",