Examine source code of Retro Youtube Filter

{
  "name": "Retro Youtube Filter",
  "version": "1.5",
  "description": "Watch Youtube Videos in Black and White",
  "manifest_version": 2,
  "permissions": [
    "https://www.youtube.com/*",
    "https://youtube.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://www.youtube.com/*",
        "https://youtube.com/*"
      ],
      "js": [
        "main.js"
      ]
    }
  ],
  "icons": {
    "16": "youtube-6-16.png",
    "48": "youtube-6-48.png",
    "64": "youtube-6-64.png",
    "128": "youtube-6-128.png",
    "256": "youtube-6-256.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{891a95e7-b21b-43ce-86dc-4d6439f94681}"
    }
  }
}