f-template custom elements are rendered in the DOM

Bug Report

The <f-template> element renders as a 0-width box in the DOM.

Repro or Code Sample

https://stackblitz.com/edit/vitejs-vite-xaylxldx?file=src%2Fmain.ts

Expected Behavior

The <f-template> itself should not be rendered in the DOM.

Current Behavior

An outline is applied to the <f-template> element, showing how the element is being rendered in the DOM:

Possible Solution

The TemplateElement should have its own embedded styles to set display: none, so it doesn't render by default.