Examine source code of Concat Selections

{
  "author": "igorlogius",
  "homepage_url": "https://github.com/igorlogius",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "512": "icon.png"
  },
  "manifest_version": 2,
  "name": "Concat Selections",
  "options_ui": {
    "page": "options.html"
  },
  "description": "Concat multiple text selections with a custom separator",
  "permissions": [
    "storage",
    "menus",
    "clipboardWrite",
    "activeTab"
  ],
  "version": "1.0.0",
  "browser_specific_settings": {
    "gecko": {
      "id": "{fa802ddb-4cdc-4ccd-8acb-8e1e80be10b7}"
    }
  }
}