fix: fix dependencies in package.json

Currently `extra-watch-webpack-plugin` is not used anymore and should be deleted from package.json.
`escape-string-regexp` is required from [bundle-config-loader](https://github.com/NativeScript/nativescript-dev-webpack/blob/master/bundle-config-loader.ts#L4) but it is not dependency of `nativescript-dev-webpack` plugin. It's working at the moment because it is dependency of [fork-ts-checker-webpack-plugin](https://github.com/NativeScript/nativescript-dev-webpack/blob/2978b81b5a8100774b2bb4a331ac8637205927b8/package.json#L54).

Author: Fatme

Diff for: package.json

@@ -50,7 +50,7 @@
     "clean-webpack-plugin": "~1.0.0",
     "copy-webpack-plugin": "~4.6.0",
     "css-loader": "~2.1.1",
-    "extra-watch-webpack-plugin": "1.0.3",
+    "escape-string-regexp": "1.0.5",
     "fork-ts-checker-webpack-plugin": "1.3.0",
     "global-modules-path": "2.0.0",
     "loader-utils": "^1.2.3",