Examine source code of Swipe two to back/forward

{
  "manifest_version": 2,
  "name": "Swipe two finger to back/forward",
  "version": "1",
  "description": "This extension enables two-finger swipe like in safari. ",
  "icons": {
    "48": "icons/icon48.png",
    "96": "icons/icon96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "touch.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background-script.js"
    ]
  },
  "options_ui": {
    "page": "options/options.html",
    "browser_style": true
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {}
  }
}