Examine source code of Print Preview Button

{
  "applications": {
    "gecko": {
      "id": "print-preview-single@codefisher.org",
      "strict_min_version": "42.0"
    }
  },
  "author": "Michael Buckley",
  "background": {
    "scripts": [
      "print-preview-background.js"
    ]
  },
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "16": "icons/16-printer-magnify.png",
      "24": "icons/24-printer-magnify.png",
      "32": "icons/32-printer-magnify.png",
      "48": "icons/48-printer-magnify.png"
    },
    "default_title": "__MSG_printPreviewLabel__"
  },
  "default_locale": "en_US",
  "description": "Open the Print Preview to view a page before printing it.\n\nPaper costs money (and trees) so it is worth checking what the page looks like before you print it.   Though it has always amazed me just how much the button gets downloaded.",
  "homepage_url": "https://codefisher.org/toolbar_button/",
  "icons": {
    "16": "icons/16-printer-magnify.png",
    "24": "icons/24-printer-magnify.png",
    "32": "icons/32-printer-magnify.png",
    "48": "icons/48-printer-magnify.png"
  },
  "manifest_version": 2,
  "name": "Print Preview Button",
  "version": "1.5resigned1"
}