fix hide/show graph window

src/roast.html

@@ -41,7 +41,7 @@
         </table>
     </div>
     <div id="graph-container" class="hidden">
-        <button id="close-btn">X</button>
+        <button onclick="hideGraph()" id="close-btn">X</button>
         <canvas id="myChart"></canvas>
     </div>
     <!--script type="module" src="./tempgraph.ts"></script-->