Where can I find what HTML and CSS SwayNC understands?

[abdulrahim-ss]

I want, in the body of the content of the notification, to send an html tag with a class name, and in style.css to configure the style of this tag. I see that, for e.g. <span>no class</span> works but not <span class="test">class</span>. Also what CSS selectors does SwayNC support?