You can access the current theme object via this.theme and it returns the object Cms\Classes\Theme, a reference to the theme customization object.
this.theme will provide direct access to form field values, defined by any theme customization. It also has the following properties natively.
Converts the theme directory name to a CSS friendly identifier.
<body class="theme-{{ this.theme.id }}">
If the theme directory was website this would generate a class name of theme-website.
An array containing all the theme configuration values found in the theme.yaml file.
<meta name="description" content="{{ this.theme.config.description }}">