Implemented stacked button groups.

lib/pixi/buttongroup.html

@@ -245,7 +245,7 @@ const buttonGroup14 = new ButtonGroup({
         {label: 'Stacked button 7', action: event => console.log('clicked 7')},
         {label: 'Stacked button 8', action: event => console.log('clicked 8')}
     ],
-    stacked: true,
+    stackPadding: 6,
     maxWidth: 620,
     app
 })
@@ -263,18 +263,30 @@ const buttonGroup15 = new ButtonGroup({
         {icon: 'battery_charging_full', type: 'checkbox', iconColorActive: 0x9c71b7}
     ],
     orientation: 'vertical',
-    margin: 0,
-    stacked: true,
+    margin: 1,
     maxHeight: 200,
     app
 })
 
+const buttons16 = []
+for (let i = 1; i < 51; i++) {
+    buttons16.push({label: `Button ${i}`, stroke: Math.floor(Math.random() * 16777215), strokeWidth: 3, radius: 16})
+}
+const buttonGroup16 = new ButtonGroup({
+    x: 90,
+    y: 1040,
+    buttons: buttons16,
+    stackPadding: 3,
+    maxWidth: 700,
+    app
+})
+
 app.scene.addChild(buttonGroup1, buttonGroup2, buttonGroup3)
 app.scene.addChild(buttonGroup4)
 app.scene.addChild(buttonGroup5, buttonGroup6)
 app.scene.addChild(buttonGroup7, buttonGroup8)
 app.scene.addChild(buttonGroup9, buttonGroup10, buttonGroup11, buttonGroup12, buttonGroup13)
-app.scene.addChild(buttonGroup14, buttonGroup15)
+app.scene.addChild(buttonGroup14, buttonGroup15, buttonGroup16)
     </script>
 </body>
 </html>