Add support for writing RTR CAN Frames to the CAN API (#1900)

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

@@ -89,6 +89,17 @@ public class CAN implements Closeable {
     CANAPIJNI.writeCANPacketRepeating(m_handle, data, apiId, repeatMs);
   }
 
+  /**
+   * Write an RTR frame to the CAN device with a specific ID. This ID is 10 bits.
+   * The length by spec must match what is returned by the responding device
+   *
+   * @param length The length to request (0 to 8)
+   * @param apiId The API ID to write.
+   */
+  public void writeRTRFrame(int length, int apiId) {
+    CANAPIJNI.writeCANRTRFrame(m_handle, length, apiId);
+  }
+
   /**
    * Stop a repeating packet with a specific ID. This ID is 10 bits.
    *