Monochrome Mode: Grayscale browsing

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 3,
  "name": "Monochrome Mode: Grayscale browsing",
  "short_name": "Monochrome Mode",
  "description": "Monochrome Mode: Grayscale browsing for focus and readability.",
  "version": "1.1.1",
  "author": "Pedro Souto",
  "background": {
    "service_worker": "js/background.js"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "js": [
        "js/content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "icons": {
    "16": "img/16-icon-monochrome-on.png",
    "32": "img/32-icon-monochrome-on.png",
    "48": "img/48-icon-monochrome-on.png",
    "128": "img/128-icon-monochrome-on.png"
  },
  "permissions": [
    "storage",
    "activeTab"
  ],
  "action": {
    "default_icon": {
      "16": "img/16-icon-monochrome-on.png",
      "32": "img/32-icon-monochrome-on.png",
      "48": "img/48-icon-monochrome-on.png",
      "128": "img/128-icon-monochrome-on.png"
    },
    "default_title": "Monochrome Mode"
  }
}