Examine source code of Twitter Web - Night Mode

{
  "manifest_version": 2,
  "name": "Twitter Web - Night Mode",
  "version": "0.0.22resigned1",
  "description": "Android/iOS like night mode for twitter web app",
  "homepage_url": "https://github.com/tsriram/twitter-web-night-mode",
  "background": {
    "scripts": [
      "js/twitter-night-mode-bg.js"
    ]
  },
  "icons": {
    "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"
    },
    {
      "matches": [
        "https://twitter.com/"
      ],
      "js": [
        "js/notification.js"
      ],
      "all_frames": false,
      "run_at": "document_end"
    }
  ],
  "web_accessible_resources": [
    "css/main.css"
  ],
  "permissions": [
    "https://twitter.com/",
    "tabs",
    "storage"
  ],
  "author": "Sriram Thiagarajan",
  "applications": {
    "gecko": {
      "id": "twitter-night-mode@mozilla.org"
    }
  }
}