[commands] Add missing PS4 triangle methods (#4576)

wpilibj/src/main/java/edu/wpi/first/wpilibj/PS4Controller.java

@@ -494,6 +494,17 @@ public class PS4Controller extends GenericHID {
     return getRawButtonReleased(Button.kTriangle.value);
   }
 
+  /**
+   * Constructs an event instance around the triangle button's digital signal.
+   *
+   * @param loop the event loop instance to attach the event to.
+   * @return an event instance representing the triangle button's digital signal attached to the
+   *     given loop.
+   */
+  public BooleanEvent triangle(EventLoop loop) {
+    return new BooleanEvent(loop, this::getTriangleButton);
+  }
+
   /**
    * Read the value of the Circle button on the controller.
    *