Added TMC2209 support (#727)

TMC2209: Added TMC2209 support

tmc2209/velocity.go

@@ -0,0 +1,12 @@
+package tmc2209
+
+func MoveAtVelocity(microstepsPerPeriod int32) {
+	// Write velocity to the relevant register
+}
+func MoveUsingStepDirInterface() {
+	// Set the interface to use step/direction interface
+}
+func GetVelocity() uint32 {
+	// Read the actual velocity register
+	return 0 // Placeholder return value
+}