Examine source code of Invert Colors

{
  "manifest_version": 2,
  "name": "Invert Colors",
  "version": "0.3.0.1",
  "author": "Max Badran",
  "description": "A simple add-on that inverts the page colors.",
  "homepage_url": "https://github.com/Max-Github/FireFoxInvertColors",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/off.svg",
    "default_title": "Invert Colors",
    "browser_style": true,
    "default_popup": "popup/options.html"
  },
  "page_action": {
    "default_icon": "icons/off.svg",
    "default_title": "Invert Current Page Colors",
    "browser_style": true
  },
  "applications": {
    "gecko": {
      "id": "@firefoxinvertcolors"
    }
  },
  "commands": {
    "global_invert": {
      "suggested_key": {
        "default": "Alt+Shift+R"
      },
      "description": "Inverts Colors Globally."
    },
    "_execute_page_action": {
      "suggested_key": {
        "default": "Alt+R"
      },
      "description": "Inverts Colors for the Current Tab."
    }
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "permissions": [
    "sessions",
    "activeTab",
    "tabs",
    "storage",
    "contextMenus",
    "<all_urls>"
  ]
}