Examine source code of Zoomimg

{
  "description": "Whenever the mouse hovers over an image, bring it into front plan for a better inspection, favorite it, set options for it or download it. Enjoy",
  "manifest_version": 2,
  "name": "Zoomimg",
  "version": "2.1.4resigned1",
  "icons": {
    "32": "icons/zoomimg-32.png",
    "48": "icons/zoomimg-48.png",
    "64": "icons/zoomimg-64.png"
  },
  "applications": {
    "gecko": {
      "id": "zoomimg@example.com"
    }
  },
  "background": {
    "scripts": [
      "libs/jquery.min.js",
      "background/background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/zoomimg-32.png",
    "default_title": "Zoomimg",
    "default_popup": "popup/zoomify.html"
  },
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "default": "Alt+1",
        "linux": "Alt+1",
        "windows": "Alt+1",
        "mac": "Alt+1"
      },
      "description": "Event that toggles the popup window"
    },
    "toggle-onoff": {
      "suggested_key": {
        "default": "Alt+2",
        "linux": "Alt+2",
        "windows": "Alt+2",
        "mac": "Alt+2"
      },
      "description": "Event that toggles the on/off of the zoom feature"
    },
    "toggle-gallery": {
      "suggested_key": {
        "default": "Alt+3",
        "linux": "Alt+3",
        "windows": "Alt+3",
        "mac": "Alt+3"
      },
      "description": "Event that toggles the gallery feature"
    },
    "toggle-favorites": {
      "suggested_key": {
        "default": "Alt+4",
        "linux": "Alt+4",
        "windows": "Alt+4",
        "mac": "Alt+4"
      },
      "description": "Event that toggles the favorites feature"
    },
    "toggle-options": {
      "suggested_key": {
        "default": "Alt+5",
        "linux": "Alt+5",
        "windows": "Alt+5",
        "mac": "Alt+5"
      },
      "description": "Event that toggles the options feature"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "libs/jquery.min.js",
        "content_scripts/zoomimg.js"
      ],
      "run_at": "document_end"
    }
  ],
  "default_locale": "en",
  "options_ui": {
    "page": "options/options.html"
  },
  "permissions": [
    "activeTab",
    "tabs",
    "storage",
    "notifications"
  ],
  "web_accessible_resources": [
    "icons/fav-star.png"
  ]
}