Reading progress indicator in minutes

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 2,
  "name": "Reading progress indicator in minutes",
  "description": "Shows reading progress in minutes left at the bottom of the page",
  "version": "1.2",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "contentscript.js"
      ]
    }
  ]
}