Examine source code of Youtube Stoplay

{
  "manifest_version": 2,
  "name": "Youtube Stoplay",
  "version": "0.0.0.1",
  "description": "Playing sound effects on YouTube when forwarding and pausing the video",
  "permissions": [
    "storage",
    "<all_urls>",
    "contextMenus"
  ],
  "icons": {
    "48": "src/icons/pause-icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*",
        "*://*.youtube-nocookie.com/*"
      ],
      "js": [
        "src/js/stoplay.js"
      ]
    }
  ]
}