For the note, Sciter (https://sciter.com) and Sciter.JS support inline vector images in its CSS.

Instead of SVG and things like FontAwesome in 99% UI cases we use just these

    button {
      background-image: url(path:M 10 10 H 90 V 90 H 10 L 10 10);
      fill: red;
    }

or

    <img src="path:M 10 10 H 90 V 90 H 10 L 10 10">