Examine source code of GridMaster for YouTube

{
  "manifest_version": 3,
  "name": "GridMaster for YouTube",
  "version": "1.0",
  "description": "Allows user to change how many items appear in a row of the YouTube feed.",
  "permissions": [
    "activeTab",
    "scripting",
    "storage",
    "webNavigation"
  ],
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icon.png"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/"
      ],
      "js": [
        "change-grid-sz.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "lucasmstephen0@gmail.com"
    }
  }
}