Examine source code of Better WebClass

{
  "manifest_version": 3,
  "name": "Better WebClass",
  "version": "0.2.2",
  "description": "WebClass の利便性を向上させる Firefox 拡張機能",
  "homepage_url": "https://github.com/liquidcatmofu/better-webclass",
  "browser_specific_settings": {
    "gecko": {
      "id": "better-webclass2@liquidcatmofu.github.io",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    },
    "gecko_android": {
      "strict_min_version": "142.0"
    }
  },
  "permissions": [
    "storage",
    "scripting",
    "alarms",
    "tabs"
  ],
  "optional_host_permissions": [
    "https://*/*"
  ],
  "background": {
    "scripts": [
      "src/background/index.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://placeholder.invalid/*"
      ],
      "js": [
        "src/content/index.js"
      ],
      "run_at": "document_end",
      "all_frames": true,
      "css": [
        "better-webclass.css"
      ]
    }
  ],
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "action": {
    "default_popup": "src/popup/index.html",
    "default_title": "Better WebClass",
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  }
}