Examine source code of Theme creator: Lite

{
  "manifest_version": 2,
  "name": "Theme creator: Lite",
  "version": "3.0",
  "permissions": [
    "theme",
    "storage",
    "<all_urls>",
    "downloads"
  ],
  "description": "Thme Creator: Lite, rapid and powerfull add-on with simple UI. Create your own themes in just one click. If you want a bigger solution with animated themes, use the full version.",
  "icons": {
    "32": "img/dark-32.png"
  },
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "16": "img/dark-16.png",
      "32": "img/dark-32.png"
    },
    "default_title": "Theme Creator: Lite",
    "default_popup": "background/background.html",
    "theme_icons": [
      {
        "light": "img/light-16.png",
        "dark": "img/dark-16.png",
        "size": 16
      },
      {
        "light": "img/light-32.png",
        "dark": "img/dark-32.png",
        "size": 32
      }
    ]
  },
  "applications": {
    "gecko": {
      "id": "lite@themecreator"
    }
  },
  "background": {
    "page": "content/loader.html"
  },
  "content_security_policy": "script-src 'self' 'unsafe-eval'; object-src 'self';"
}