Examine source code of Étude — Loop & Slow Down YouTube for Practice

{
  "manifest_version": 3,
  "name": "Étude — Loop & Slow Down YouTube for Practice",
  "description": "Practice tools for YouTube — loop a section, slow it down, zoom in for precision. Made for musicians learning by ear.",
  "version": "0.4.0",
  "short_name": "Étude",
  "icons": {
    "16": "icon/16.png",
    "32": "icon/32.png",
    "48": "icon/48.png",
    "96": "icon/96.png",
    "128": "icon/128.png"
  },
  "permissions": [
    "storage"
  ],
  "host_permissions": [
    "https://www.youtube.com/*"
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "fonts/*"
      ],
      "matches": [
        "https://www.youtube.com/*"
      ]
    },
    {
      "resources": [
        "content-scripts/content.css"
      ],
      "use_dynamic_url": true,
      "matches": [
        "https://www.youtube.com/*"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "etude@ed1001.dev",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_title": "Étude",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.youtube.com/*"
      ],
      "js": [
        "content-scripts/content.js"
      ]
    }
  ]
}