Examine source code of Refers.To Link Shrinker

{
  "name": "Refers.To Link Shrinker",
  "description": "Shortens URLs to the clipboard",
  "version": "0.2.8resigned1",
  "permissions": [
    "contextMenus",
    "clipboardWrite"
  ],
  "background": {
    "scripts": [
      "event.js"
    ]
  },
  "manifest_version": 2,
  "icons": {
    "16": "refers.to16.png",
    "48": "refers.to48.png",
    "128": "refers.to128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{405d4798-8a01-4f4c-92a7-ddc56845de12}"
    }
  }
}