Provide vscode configs

[trickypr]

There are a number of mozilla files that are just python files (e.g. moz.build). It would be ideal for these to be highlighted by their relevant syntax highlighter. For example:

// .vscode/settings.json
{
  "files.associations": {
    "*.jsm": "javascript",
    "moz.build": "python",
    "moz.configure": "python",
    "app.mozbuild": "python",
    "Makefile.in": "makefile",
    "mozconfig": "shellscript"
  }
}

[ajvincent]

I would welcome a pull request for this.