function addStylesheet(resourceName) {
		var oLink = document.createElement("link");
		oLink.rel = "stylesheet";
		oLink.href = sap.ui.require.toUrl(resourceName);
		document.head.appendChild(oLink);
	}
Adds a stylesheet to the head.

sap/ui/dom/includeStylesheet requires additional modules, so we don't use it here.
@param {string} resourceName UI5 resource name of the stylesheet (not a URL!)