Material Design - Custom Dark Mode

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 2,
  "name": "Material Design - Custom Dark Mode",
  "description": "Load custom css to set dark mode for some websites.",
  "version": "1.0.1",
  "author": "Arnout Pullen",
  "browser_action": {
    "default_icon": "assets/material-icon-128-128.png",
    "default_title": "Dark Mode"
  },
  "content_scripts": [
    {
      "matches": [
        "https://*.tweakers.net/*"
      ],
      "css": [
        "sites/tweakers/tweakers.css"
      ]
    },
    {
      "matches": [
        "https://9gag.com/*"
      ],
      "css": [
        "sites/9gag/9gag.css"
      ]
    }
  ],
  "icons": {
    "16": "assets/material-icon-16-16.png",
    "32": "assets/material-icon-32-32.png",
    "48": "assets/material-icon-48-48.png",
    "128": "assets/material-icon-128-128.png"
  }
}