Examine source code of Twitter Web - Flat Night Theme

{
  "manifest_version": 2,
  "name": "Twitter Web - Flat Night Theme",
  "version": "0.1.3resigned1",
  "description": "Don't like the standard look of the twitter website? Are you a fan of flat design? Enjoy 'night mode' on the mobile twitter app? Well you're in luck! Thanks to this extension the twitter website looks more flat designed and improves the general look of twitter! It also adds the 'night mode' available in the mobile twitter app",
  "homepage_url": "http://brinecraft.xyz/extensions/firefox/twitter-flat-design",
  "background": {
    "scripts": [
      "js/twitter-night-mode-bg.js"
    ]
  },
  "icons": {
    "16": "images/icon16.png",
    "32": "images/icon32.png",
    "128": "images/icon128.png"
  },
  "browser_action": {
    "browser_style": true,
    "default_popup": "popup/info.html",
    "default_icon": {
      "16": "images/icon16.png",
      "32": "images/icon32.png",
      "128": "images/icon128.png"
    }
  },
  "page_action": {
    "default_icon": "images/icon32.png",
    "default_title": "Extension will be enabled when you open twitter.com"
  },
  "content_scripts": [
    {
      "matches": [
        "https://twitter.com/*",
        "https://twitter.com/",
        "https://twitter.com/i/cards/*"
      ],
      "js": [
        "js/twitter-night-mode.js"
      ],
      "all_frames": true,
      "run_at": "document_start"
    }
  ],
  "web_accessible_resources": [
    "css/main.css"
  ],
  "permissions": [
    "https://twitter.com/",
    "tabs",
    "storage"
  ],
  "author": "DerpCraftyBuoy",
  "applications": {
    "gecko": {
      "id": "twitter-flat-design@brinecraft.xyz"
    }
  }
}