Add SingleStoreDB to demo page

Author: nene

static/index.html

@@ -66,6 +66,7 @@ <h3 style="margin: 0.5rem 0">Options</h3>
               <option value="n1ql">N1QL</option>
               <option value="plsql">PL/SQL</option>
               <option value="postgresql">PostgreSQL</option>
+              <option value="singlestoredb">SingleStoreDB</option>
               <option value="spark">Spark</option>
               <option value="sqlite">SQLite</option>
               <option value="tsql">Transact-SQL</option>