Examine source code of Group Running Tracker

{
  "manifest_version": 2,
  "name": "Group Running Tracker",
  "version": "1.0",
  "description": "Create running groups, add friends, and track your progress together.",
  "permissions": [],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "128": "images/group-logo.png"
    }
  },
  "icons": {
    "128": "images/group-logo.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{d8d09afb-3dfe-48b1-938f-203dfd991534}"
    }
  }
}