Examine source code of Omni - Manage Tabs, Bookmarks, History...

{
  "name": "Omni",
  "description": "Supercharge Firefox with commands, shortcuts, and more",
  "version": "1.4.5",
  "manifest_version": 2,
  "browser_action": {
    "default_icon": {
      "16": "assets/logo-16.png",
      "48": "assets/logo-48.png",
      "128": "assets/logo-128.png"
    }
  },
  "icons": {
    "16": "assets/logo-16.png",
    "48": "assets/logo-48.png",
    "128": "assets/logo-128.png"
  },
  "commands": {
    "open-omni": {
      "suggested_key": {
        "default": "Ctrl+Shift+K",
        "mac": "Command+Shift+K"
      },
      "description": "Open command menu"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_end",
      "js": [
        "focus.js",
        "jquery.js",
        "content.js",
        "virtualized-list.min.js"
      ],
      "css": [
        "content.css"
      ]
    }
  ],
  "web_accessible_resources": [
    "content.html",
    "newtab.html",
    "assets/*",
    "popup.css",
    "popup.js"
  ],
  "permissions": [
    "tabs",
    "activeTab",
    "bookmarks",
    "browsingData",
    "history",
    "search"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{5bc8d6f7-79e6-42b0-a64e-06a05dc2db5d}"
    }
  }
}