Examine source code of Textutils

{
  "name": "Textutils",
  "description": "A text utility to change character into Uppercase, Lowercase, and much more...",
  "version": "1.0",
  "manifest_version": 2,
  "browser_action": {
    "default_popup": "index.html",
    "default_icon": "images/logo.png"
  },
  "icons": {
    "16": "images/logo_16.png",
    "48": "images/logo_48.png",
    "96": "images/logo_96.png",
    "128": "images/logo_128.png"
  }
}