replaced \n with whitespace

lib/single-file/serializer.js

@@ -70,7 +70,7 @@ this.serializer = this.serializer || (() => {
 				docTypeString += " SYSTEM \"" + docType.systemId + "\"";
 			if (docType.internalSubset)
 				docTypeString += " [" + docType.internalSubset + "]";
-			return docTypeString + ">\n";
+			return docTypeString + "> ";
 		}
 		return "";
 	}