copy/paste prevention

lib/single-file/serializer.js

@@ -120,7 +120,7 @@ this.serializer = this.serializer || (() => {
 				value = Array.from(element.classList).map(className => className.trim()).join(" ");
 			}
 			value = value.replace(/&/g, "&").replace(/\u00a0/g, " ").replace(/"/g, """);
-			const invalidUnquotedValue = !value.match(/^[^ \t\n\f\r'`=<>]+$/);
+			const invalidUnquotedValue = !value.match(/^[^ \t\n\f\r'"`=<>]+$/);
 			content += " ";
 			if (!attribute.namespace) {
 				content += name;