Bundling topic doesn't include the necessary information to enable debugging

[neilenns]

The Bundling Extension topic explains how to get webpack up and running, but leaves out important information that results in a broken debug configuration.

Specifically the following information is missing:

1. The watch script needs to include --info-verbosity verbose when calling webpack
2. The tasks.json file needs to include the $ts-webpack-watch problem matcher
3. I believe (but am not 100% sure) tasks.json should also include "isBackground": true
4. Developers need to install the Typescript & Webpack Problem Matchers extension

It would be useful to include a complete launch.json file as well to show the change to using the dist folder:

  "version": "0.2.0",
  "configurations": [
    {
      "name": "Run Extension",
      "type": "extensionHost",
      "request": "launch",
      "runtimeExecutable": "${execPath}",
      "args": ["--extensionDevelopmentPath=${workspaceFolder}"],
      "outFiles": ["${workspaceFolder}/dist/**/*.js"],
      "preLaunchTask": "${defaultBuildTask}"
    }
  ]
}```