Examine source code of Reddit Filter by Comments

{
  "manifest_version": 2,
  "name": "Reddit Filter by Comments",
  "version": "1.0",
  "description": "Hides Reddit posts with more than selected number of comments.",
  "icons": {
    "48": "icons/comments-48.png"
  },
  "permissions": [
    "activeTab",
    "tabs",
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "redditfilter@bycomments.number"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://old.reddit.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_action": {
    "default_popup": "popup.html"
  }
}