Examine source code of Pinned Messenger

{
  "applications": {
    "gecko": {
      "id": "fbmessengerpanel@alejandrobrizuela.com.ar"
    }
  },
  "manifest_version": 2,
  "name": "Pinned Messenger",
  "version": "2.1.1",
  "description": "Go to the pinned Messenger tab. If it doesn't exist, it's created.",
  "icons": {
    "48": "icons/messenger-48.png",
    "64": "icons/messenger-64.png"
  },
  "permissions": [
    "tabs"
  ],
  "browser_action": {
    "default_icon": {
      "32": "icons/messenger-32.png"
    },
    "default_title": "Pinned Messenger",
    "default_area": "navbar"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "default": "Alt+Shift+M"
      }
    }
  },
  "options_ui": {
    "page": "options/options.html",
    "browser_style": true
  }
}