Examine source code of Selection menu

{
  "manifest_version": 3,
  "name": "Selection Menu",
  "version": "3.1.0",
  "description": "Pop-up menu after selection with copying and searching for selected text in Google (or other search engines)",
  "homepage_url": "https://github.com/mad1ost/selection-menu",
  "icons": {
    "32": "icons/icon-32.png",
    "64": "icons/icon-64.png",
    "128": "icons/icon-128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "js": [
        "selection-menu.js"
      ],
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_end",
      "all_frames": false
    },
    {
      "js": [
        "selection-menu-sub.js"
      ],
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_end",
      "all_frames": true
    }
  ],
  "options_ui": {
    "page": "options.html"
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{c3f89c61-f1ef-4f14-a7d6-49aff242663f}",
      "strict_min_version": "109.0"
    }
  }
}