Check webpack use in build process

[GehDoc]

• Webpacked files are missing from 'package' and 'publish' commands.
  Idea : Webpack should be called by gulp in the sequence, not by vscode task.
• Look at integration with nls :
  • https://github.com/microsoft/vscode-extension-samples/tree/master/webpack-sample
  • And, verify : https://code.visualstudio.com/api/working-with-extensions/bundling-extension