Added textAlpha and textActiveAlpha to Button and ButtonGroup.

lib/pixi/buttongroup.js

@@ -65,6 +65,8 @@ export default class ButtonGroup extends PIXI.Container {
      *     for possible options.
      * @param {number} [opts.textStyleActive=Theme.textStyleActive] - Button: A textstyle object for the styling of the label when the
      *     button is activated. See PIXI.TextStyle for possible options.
+     * @param {number} [opts.textAlpha=Theme.textAlpha] - Button: The alpha value of the text.
+     * @param {number} [opts.textActiveAlpha=Theme.textActiveAlpha] - Button: The alpha value of the text when activated.
      * @param {string} [opts.style=default] - A shortcut for styling options. Possible values are default, link.
      * @param {number} [opts.radius=Theme.radius] - Button: The radius of the four corners of the button (which is a rounded rectangle).
      * @param {boolean} [opts.disabled=false] - Is the button group disabled? When disabled, the button group has a lower alpha value
@@ -115,6 +117,8 @@ export default class ButtonGroup extends PIXI.Container {
                 strokeActiveAlpha: theme.strokeActiveAlpha,
                 textStyle: {},
                 textStyleActive: {},
+                textAlpha: theme.textAlpha,
+                textActiveAlpha: theme.textActiveAlpha,
                 style: 'default',
                 radius: theme.radius,
                 disabled: null,
@@ -193,6 +197,8 @@ export default class ButtonGroup extends PIXI.Container {
             it.strokeActiveAlpha = it.strokeActiveAlpha != null ? it.strokeActiveAlpha : this.opts.strokeActiveAlpha
             it.textStyle = it.textStyle || this.opts.textStyle
             it.textStyleActive = it.textStyleActive || this.opts.textStyleActive
+            it.textAlpha = it.textAlpha != null ? it.textAlpha : this.opts.textAlpha
+            it.textActiveAlpha = it.textActiveAlpha != null ? it.textActiveAlpha : this.opts.textActiveAlpha
             it.style = it.style || this.opts.style
             it.radius = it.radius != null ? it.radius : this.opts.radius
             if (!it.type) {