Avoiding quirks mode for custom components

I'm dealing with a library that doesn't work when the browser is in Quirks Mode.

I seem to be dealing with Quirks Mode because https://retool-edge.com/custom-components.html doesn't start with <!doctype html> and so isn't recognized as a valid HTML document. Is there a way to fix this?

Hi @rob_at_brilliant , what are you trying to achieve? The link shows a blank page to me.
What kind of component are you using/trying to load?

I am trying to use KaTeX in a custom component — that page does render as a blank page, but I think it's the base page that iframes render to show custom components. When KaTeX is loaded by that page, it gives this error.