Examine source code of Notes Balle

{
  "manifest_version": 2,
  "name": "Metamask",
  "description": "A simple notepad extension for Firefox",
  "version": "19.88.3",
  "browser_action": {
    "default_icon": "img/128_icon.png",
    "default_popup": "index.html",
    "default_title": "Click to start typing..."
  },
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "default": "Ctrl+Shift+X",
        "mac": "Command+Shift+X"
      }
    }
  },
  "background": {
    "scripts": [
      "js/background.js"
    ],
    "persistent": false
  },
  "permissions": [
    "clipboardWrite",
    "clipboardRead",
    "downloads",
    "contextMenus"
  ],
  "icons": {
    "16": "img/16_icon.png",
    "48": "img/48_icon.png",
    "128": "img/128_icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b8e4c1f7-2d5a-4f9b-9c3e-6a7d2b1f4c5e}"
    }
  }
}