Fixed theming bug in button and button group.

lib/pixi/button.html

@@ -32,7 +32,7 @@
 const app = new PIXIApp({
     view: canvas,
     width: 900,
-    height: 520,
+    height: 600,
     transparent: false
 }).setup().run()
 
@@ -309,6 +309,17 @@ setInterval(() => {
     button25.layout()
 }, 1000)
 
+const button26 = new Button({
+    x: 10,
+    y: 520,
+    label: 'add',
+    type: 'checkbox',
+    strokeActive: 0x28a745,
+    textStyleActive: {
+        fill: 0x28a745
+    }
+})
+
 app.scene.addChild(button1, button2, button3, button4, button5, button6)
 app.scene.addChild(button7, button8)
 app.scene.addChild(button9, button10, button11)
@@ -316,6 +327,7 @@ app.scene.addChild(button12, button13)
 app.scene.addChild(button14, button15, button16, button17)
 app.scene.addChild(button18, button19, button20, button21)
 app.scene.addChild(button22, button23, button24, button25)
+app.scene.addChild(button26)
     </script>
 </body>
 </html>