Examine source code of Wall Clock

{
  "manifest_version": 3,
  "name": "Wall-Clock",
  "version": "1.0.1",
  "description": "",
  "homepage_url": "https://github.com/OkanoShinri/wall-clock",
  "browser_specific_settings": {
    "gecko": {
      "id": "wallclock@example.com"
    }
  },
  "icons": {
    "128": "icons/128.png"
  },
  "permissions": [
    "activetab",
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "src/content_scripts/content.js"
      ],
      "css": [
        "src/content_scripts/style.css"
      ]
    }
  ],
  "action": {
    "default_icon": "icons/128.png",
    "default_popup": "src/popup/popup.html"
  },
  "options_ui": {
    "page": "src/option/options.html",
    "open_in_tab": true
  },
  "background": {
    "scripts": [
      "src/background-scripts/background.js"
    ]
  }
}