Examine source code of PushNote

{
  "manifest_version": 2,
  "name": "PushNote",
  "version": "1.0",
  "description": "Send messages via Pushover.",
  "icons": {
    "48": "icons/pushnote.png"
  },
  "browser_action": {
    "default_popup": "PushNote.html",
    "default_icon": "icons/pushnote.png"
  },
  "permissions": [
    "activeTab",
    "storage",
    "http://*/*",
    "https://*/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{b3dfcbeb-3716-43e5-80f1-88f71d3a8b91}"
    }
  }
}