Examine source code of Better Twitter

{
  "name": "Better Twitter",
  "version": "2.1.3",
  "description": "Hide what's not important on Twitter.com",
  "manifest_version": 2,
  "applications": {
    "gecko": {
      "id": "{ef32ca60-1728-4011-a585-4de439fe7ba7}"
    }
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false,
    "browser_style": true,
    "chrome_style": true
  },
  "icons": {
    "64": "icon-64.png",
    "128": "icon-128.png"
  },
  "browser_action": {
    "browser_style": true,
    "default_popup": "options.html"
  },
  "permissions": [
    "storage"
  ],
  "web_accessible_resources": [
    "options.js",
    "prefs.js"
  ],
  "content_scripts": [
    {
      "run_at": "document_start",
      "matches": [
        "https://twitter.com/*",
        "https://mobile.twitter.com/*",
        "https://x.com/*",
        "https://*.x.com/*"
      ],
      "css": [
        "content.css"
      ],
      "js": [
        "utils.js",
        "prefs.js",
        "content.js"
      ]
    }
  ]
}