Examine source code of YT Declutter-er

{
  "manifest_version": 2,
  "name": "YT Declutter",
  "version": "0.2.0",
  "description": "Declutter YouTube by hiding unwanted content",
  "homepage_url": "https://github.com/ammuench/yt-declutter",
  "icons": {
    "16": "icon-16.png",
    "48": "icon-48.png",
    "128": "icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "yt-declutter@ammuench.github.io",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "*://www.youtube.com/*",
    "*://youtube.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*",
        "*://youtube.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "content.css"
      ],
      "run_at": "document_start"
    }
  ],
  "web_accessible_resources": [
    "content.css"
  ]
}