Examine source code of Font Customizer Basic

{
  "manifest_version": 2,
  "name": "Font Customizer Basic",
  "version": "1.0",
  "description": "Customize font style and size to improve readability on websites.",
  "permissions": [],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "128": "images/font-logo.png"
    }
  },
  "icons": {
    "128": "images/font-logo.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{07a3bd22-c48c-4cc4-a3ee-83b95e2e32d5}"
    }
  }
}