Examine source code of 2 clicks to select

{
  "browser_specific_settings": {
    "gecko": {
      "id": "2c2s@snca.net",
      "strict_min_version": "42.0"
    }
  },
  "manifest_version": 2,
  "version": "0.1.0",
  "short_name": "2c2s",
  "name": "2 clicks to select",
  "description": "Click a word twice to select text",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "main.js"
      ],
      "all_frames": true
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "options.html"
  },
  "permissions": [
    "storage"
  ],
  "icons": {
    "48": "icon/kuri.48x48.png",
    "64": "icon/kuri.64x64.png",
    "72": "icon/kuri.72x72.png",
    "96": "icon/kuri.96x96.png",
    "128": "icon/kuri.128x128.png",
    "144": "icon/kuri.144x144.png",
    "152": "icon/kuri.152x152.png",
    "192": "icon/kuri.192x192.png",
    "384": "icon/kuri.384x384.png",
    "512": "icon/kuri.512x512.png"
  }
}