[wpimath] Add an operator for composing two Transform2ds (#3527)

wpimath/src/main/java/edu/wpi/first/math/geometry/Transform2d.java

@@ -56,6 +56,15 @@ public class Transform2d {
     return new Transform2d(m_translation.times(scalar), m_rotation.times(scalar));
   }
 
+  /**
+   * Composes two transformations.
+   *
+   * @param other The transform to compose with this one.
+   */
+  public Transform2d plus(Transform2d other) {
+    return new Transform2d(new Pose2d(), new Pose2d().transformBy(this).transformBy(other));
+  }
+
   /**
    * Returns the translation component of the transformation.
    *