Examine source code of Your Custom Css

{
  "manifest_version": 2,
  "name": "Your Css",
  "version": "1.0",
  "permissions": [
    "scripting",
    "storage",
    "activeTab"
  ],
  "description": "Add and save your own custom css for whatever websites you want.",
  "browser_specific_settings": {
    "gecko": {
      "id": "{c6ed5221-147e-4103-b238-1617a7894130}",
      "strict_min_version": "102.0"
    }
  },
  "icons": {
    "48": "icons/your-css-logo.png"
  },
  "browser_action": {
    "default_icon": "icons/your-css-logo.png",
    "default_title": "your-css",
    "default_popup": "index.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "./scripts/your-css.js"
      ]
    }
  ],
  "options_ui": {
    "page": "import-listing.html",
    "open_in_tab": true
  }
}