fix: Adds type attr. to the generated link element

Although the rel element is set to stylesheet the created link element does not specify the MIME type of the linked resource.
The MIME type is set to text/css similar to the case when an style element is created. This change also syncs with the addStylesUrl.js behavior where the type attribute is set.

addStyles.js

@@ -136,6 +136,7 @@ function createStyleElement(options) {
 function createLinkElement(options) {
 	var linkElement = document.createElement("link");
 	linkElement.rel = "stylesheet";
+	linkElement.type = "text/css";
 	insertStyleElement(options, linkElement);
 	return linkElement;
 }