[wpilib] Tachometer: Add function to return RPS (#3833)

wpilibc/src/main/native/include/frc/counter/Tachometer.h

@@ -75,6 +75,15 @@ class Tachometer : public wpi::Sendable,
    */
   void SetEdgesPerRevolution(int edges);
 
+  /**
+   * Gets the current tachometer revolutions per second.
+   *
+   * SetEdgesPerRevolution must be set with a non 0 value for this to work.
+   *
+   * @return Current RPS.
+   */
+  units::turns_per_second_t GetRevolutionsPerSecond() const;
+
   /**
    * Gets the current tachometer revolutions per minute.
    *