add decoder for tracked point position submodule

src/decoders/index.ts

@@ -1,11 +1,13 @@
 import CentroidPosition from './motion/centroid-position';
 import OrientationEuler from './motion/orientation-euler';
 import OrientationQuaternion from './motion/orientation-quaternion';
+import TrackedPointPosition from './motion/tracked-point-position';
 import RTTrPHeader from './rttrp';
 
 export const Decoders = {
   RTTrPHeader,
   CentroidPosition,
+  TrackedPointPosition,
   OrientationQuaternion,
   OrientationEuler,
 };