Examine source code of GitHub Snake Game

{
  "manifest_version": 2,
  "name": "GitHub Snake Game",
  "version": "0.3.2",
  "description": "Play Snake on your GitHub contribution graph.",
  "permissions": [
    "activeTab",
    "notifications"
  ],
  "background": {
    "scripts": [
      "extension-activate.js"
    ]
  },
  "browser_action": {
    "default_title": "Play (Keys: W, A, S, D)",
    "default_icon": {
      "16": "icon.png",
      "48": "icon.png",
      "128": "icon.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{815c2016-7f56-4638-982c-0504e3d3bb9f}"
    }
  }
}