use simple quotes xhen possible

lib/single-file/serializer.js

@@ -118,7 +118,15 @@ this.serializer = this.serializer || (() => {
 			if (name == "class") {
 				value = Array.from(element.classList).map(className => className.trim()).join(" ");
 			}
-			value = value.replace(/&/g, "&").replace(/\u00a0/g, " ").replace(/"/g, """);
+			let simpleQuotesValue;
+			value = value.replace(/&/g, "&").replace(/\u00a0/g, " ");
+			if (value.includes("\"")) {
+				if (value.includes("'")) {
+					value = value.replace(/"/g, """);
+				} else {
+					simpleQuotesValue = true;
+				}
+			}
 			const invalidUnquotedValue = !value.match(/^[^ \t\n\f\r'"`=<>]+$/);
 			content += " ";
 			if (!attribute.namespace) {
@@ -138,11 +146,11 @@ this.serializer = this.serializer || (() => {
 			if (value != "") {
 				content += "=";
 				if (invalidUnquotedValue) {
-					content += "\"";
+					content += simpleQuotesValue ? "'" : "\"";
 				}
 				content += value;
 				if (invalidUnquotedValue) {
-					content += "\"";
+					content += simpleQuotesValue ? "'" : "\"";
 				}
 			}
 		}