StaticHTMLRenderer fix height

[ThijsBroersen]

Regarding the work-around to fix the height of an iframe:
I experienced issues in jupyter-lab with the height so I started debugging and wrote a custom method to get my html. The new iframe used an onload function which is just an attribute (so no issues with sandbox allow-this-that bla bla.
Could you please also fix the ConfigDSL, it currently returns a partial function...

val renderer = StaticHTMLRenderer(builder.config(background = "white")(builder).toJson)
val html = s"""
        | <iframe 
        | style="border: none; width: 100%" 
        | onload='(function(e){setTimeout(function() { e.style.height = e.contentDocument.firstElementChild.scrollHeight + "px"}, 200)})(this);' 
        | srcdoc="${xml.Utility.escape(renderer.pageHTML())}"></iframe>
        """.stripMargin