Examine source code of Badge Checker for Gmail™

{
  "version": "0.1.6",
  "manifest_version": 3,
  "name": "Badge Checker for Gmail™",
  "host_permissions": [
    "*://*.mail.google.com/*"
  ],
  "homepage_url": "https://mybrowseraddon.com/badge-checker-for-gmail.html",
  "description": "Shows badge notification for unread emails (supports multi-account)",
  "commands": {
    "_execute_action": {}
  },
  "permissions": [
    "alarms",
    "storage"
  ],
  "options_ui": {
    "open_in_tab": true,
    "page": "data/options/options.html"
  },
  "web_accessible_resources": [
    {
      "matches": [
        "*://*.mail.google.com/*"
      ],
      "resources": [
        "data/content_script/page_context/*"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "strict_min_version": "109.0",
      "id": "{ffb11de0-4587-475f-8a33-6904d5f95f45}"
    }
  },
  "background": {
    "scripts": [
      "lib/config.js",
      "lib/chrome.js",
      "lib/runtime.js",
      "lib/common.js",
      "lib/vendor/from-xml.js"
    ]
  },
  "action": {
    "default_title": "Badge Checker for Gmail",
    "default_icon": {
      "16": "data/icons/16.png",
      "32": "data/icons/32.png",
      "48": "data/icons/48.png",
      "64": "data/icons/64.png"
    }
  },
  "content_scripts": [
    {
      "all_frames": false,
      "run_at": "document_start",
      "matches": [
        "*://*.mail.google.com/*"
      ],
      "js": [
        "data/content_script/inject.js"
      ]
    }
  ],
  "icons": {
    "16": "data/icons/16.png",
    "32": "data/icons/32.png",
    "48": "data/icons/48.png",
    "64": "data/icons/64.png",
    "128": "data/icons/128.png"
  }
}