Examine source code of Select By Domain

{
  "name": "Select By Domain",
  "version": "0.1.1",
  "description": "Select all tabs from the same domain",
  "icons": {
    "16": "assets/icon016.png",
    "24": "assets/icon024.png",
    "32": "assets/icon032.png"
  },
  "developer": {
    "name": "Martijn van der Ven",
    "url": "https://vanderven.se/martijn/"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "manifest_version": 2,
  "permissions": [
    "tabs",
    "contextMenus"
  ],
  "browser_specific_settings": {
    "gecko": {
      "strict_min_version": "77.0"
    }
  }
}