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

wpimath/src/main/native/include/frc/geometry/Transform2d.h

@@ -81,6 +81,13 @@ class Transform2d {
     return Transform2d(m_translation * scalar, m_rotation * scalar);
   }
 
+  /**
+   * Composes two transformations.
+   *
+   * @param other The transform to compose with this one.
+   */
+  Transform2d operator+(const Transform2d& other) const;
+
   /**
    * Checks equality between this Transform2d and another object.
    *