Examine source code of Hello World

{
  "theme": {
    "images": {
      "theme_frame": "helloworldheader.jpg"
    },
    "colors": {
      "frame": "#e8a02c",
      "tab_background_text": "#fafafa"
    }
  },
  "version": "2.0",
  "name": "Hello World",
  "manifest_version": 2,
  "description": "Let your Firefox say hello to the world! :)"
}