Add trajectory generation using hermite splines (#1843)

wpilibc/src/main/native/include/frc/geometry/Rotation2d.h

@@ -97,6 +97,14 @@ class Rotation2d {
    */
   Rotation2d operator-() const;
 
+  /**
+   * Multiplies the current rotation by a scalar.
+   * @param scalar The scalar.
+   *
+   * @return The new scaled Rotation2d.
+   */
+  Rotation2d operator*(double scalar) const;
+
   /**
    * Checks equality between this Rotation2d and another object.
    *