Examine source code of Reading Time Estimator

{
  "manifest_version": 2,
  "name": "Reading Time Estimator",
  "version": "1.0",
  "description": "An extension to estimate reading time.",
  "permissions": [],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{77858372-b46d-40dc-b78a-6ab62997eb11}"
    }
  }
}