Examine source code of Walling Web Clipper

{
  "name": "Walling Web Clipper",
  "short_name": "Walling",
  "description": "Jot down quick notes, save bookmarks and images to your Walling.app Daily Desk and Walls.",
  "version": "1.2.65",
  "manifest_version": 2,
  "icons": {
    "16": "icons/icon_16.png",
    "32": "icons/icon_32.png",
    "48": "icons/icon_48.png",
    "128": "icons/icon_128.png"
  },
  "browser_action": {
    "default_title": "Walling Web Clipper",
    "default_icon": "icons/icon_48.png",
    "default_popup": "popup/popup.html"
  },
  "web_accessible_resources": [
    "popup/images/*",
    "images/*",
    "*.ttf"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "activeTab",
    "contextMenus",
    "storage"
  ],
  "content_security_policy": "script-src 'self' 'unsafe-eval' https://apis.google.com; object-src 'self'",
  "browser_specific_settings": {
    "gecko": {
      "id": "{5535be49-c7b3-47ea-ad07-c6f454d69e57}"
    }
  }
}