Examine source code of Feed Blocker

{
  "manifest_version": 2,
  "name": "Feed Blocker",
  "short_name": "Feed Blocker",
  "version": "1.2",
  "description": "Blocks Telegram chat items and YouTube feed.",
  "permissions": [
    "*://*.telegram.org/*",
    "*://*.youtube.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.telegram.org/*"
      ],
      "js": [
        "telegram.js"
      ],
      "run_at": "document_start"
    },
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "youtube.js"
      ],
      "css": [
        "youtube.css"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{ed34459f-78c4-409e-8b6f-bfcc772de6b9}"
    }
  }
}