Examine source code of Squoosh

{
  "manifest_version": 2,
  "name": "Squoosh",
  "description": "Displays a sidebar for Google's Squoosh web app.",
  "version": "1.0.2",
  "author": "AnalogCyan",
  "developer": {
    "name": "AnalogCyan",
    "url": "https://github.com/AnalogCyan/"
  },
  "sidebar_action": {
    "default_icon": "icons/logo.af355.svg",
    "default_title": "Squoosh",
    "default_panel": "sidebar/panel.html",
    "browser_style": true
  },
  "icons": {
    "48": "icons/logo.af355.svg"
  },
  "offline_enabled": true,
  "permissions": [
    "storage"
  ]
}