Examine source code of YouCaptain

{
  "name": "YouCaptain",
  "version": "0.0.12",
  "description": "Enables keyboard navigation on YouTube",
  "manifest_version": 2,
  "homepage_url": "https://github.com/glaucocustodio/youcaptain",
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "css": [
        "style.css"
      ],
      "run_at": "document_end",
      "js": [
        "content_script.js"
      ]
    }
  ],
  "options_ui": {
    "page": "options.html"
  },
  "web_accessible_resources": [
    "spatial_navigation.js",
    "main.js",
    "button.wav"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "permissions": [
    "tabs",
    "storage"
  ],
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  }
}