chore: remove webpack.config.js files from demo apps

As the demo apps are now using custom webpack.config.js files, they no longer need the default webpack.config.js files. They'll be managed by the installation of nativescript-dev-webpack

Author: rosen-vladimirov

demo/.gitignore

@@ -17,4 +17,5 @@ vendor.js
 vendor.ts
 
 tsconfig.esm.json
-mochawesome-report
+mochawesome-report
+webpack.config.js