How to use Material Icons in Vaadin 14+ ?

Flow
1

I want to use MaterialIcons in Vaadin 14+. Give an example to setup project and use that.
I am using MaterialIcons getHtml method but its not working as expected.

Span span = new Span();
span.add(new Html(MaterialIcons.CALL_MERGE.getHtml()));

But this is not showing any icon.