adding xsd to prefix constants

Author: falcontologist

shacl-demo/js/app.js

@@ -33,6 +33,7 @@ const PREFIXES = `@prefix :    <https://falcontologist.github.io/shacl-demo/onto
 @prefix temp: <${CONFIG.TEMP_NS}> .
 @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
 @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
+@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
 
 `;