add adoptedStyleSheets to the options

[rhildred]

When options.shadow == true, it would be helpful to add to adoptedStyleSheets so that one can have scoped css.

const sheet = new CSSStyleSheet();
sheet.replaceSync("h1 { color: blue; border: 2px dotted black;}");


register(App, "x-rich", [], {shadow:true, adoptedStyleSheets:[sheet]});