Examine source code of SideTwitch

{
  "manifest_version": 2,
  "name": "SideTwitch",
  "description": "Embed Twitch in your browser",
  "version": "1.0.1resigned1",
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "js": [
        "lib/twitch-v1.js",
        "js/wrapper.js"
      ],
      "run_at": "document_end",
      "css": [
        "css/wrapper.css"
      ]
    }
  ],
  "browser_action": {
    "default_icon": "img/favicon.png",
    "default_title": "Twitch Sideplayer",
    "default_popup": "html/popup.html"
  },
  "background": {
    "scripts": [
      "js/background.js"
    ]
  },
  "commands": {
    "toggle-display": {
      "suggested_key": {
        "default": "Alt+Shift+T"
      },
      "description": "Toggle Twitch Iframe display"
    }
  },
  "web_accessible_resources": [
    "html/wrapper.html",
    "css/wrapper.css",
    "img/x-circle.svg",
    "img/move.svg",
    "img/play-button.png"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{b7adf8aa-8da6-47bb-9912-cff3211bd47b}"
    }
  }
}