Examine source code of Simple Invert Colors

{
  "manifest_version": 2,
  "name": "Invert Colors",
  "version": "1.0",
  "description": "Inverts page colors when clicked or via keyboard shortcut",
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "invert-colors@sugarpine.cafe",
      "data_collection_permissions": {
        "data_collected": false,
        "required": [
          "none"
        ]
      }
    }
  },
  "browser_action": {
    "default_title": "Invert Colors",
    "default_icon": "icon.svg"
  },
  "background": {
    "scripts": [
      "invert-colors.js"
    ]
  },
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "default": "Alt+Shift+I"
      },
      "description": "Invert page colors"
    }
  }
}