add info on modality to CHANGES.md

[ci skip]

CHANGES.md

@@ -2,23 +2,22 @@
 
 ## v3.3.0
 
-* SPECTUBMatrix for (simple) usage in SPECT added.
+* Added a new acquisition model `SPECTUBMatrix` for (simple) usage in SPECT.
+  `sirf.STIR.ImageData` has now a way to set/get the modality.
 
 * interactive Python demos superseded by SIRF-Exercises notebooks removed.
 
 * arguments setting number of CG iterations and verbosity of output
-  of acquisition models method norm() added.
+  of acquisition models method `norm()` added.
 
 * path for ISMRMRD shared library when generating MR data fixed.
 
-* extension processing in ISMRMRDImageData::write fixed.
+* extension processing in `ISMRMRDImageData::write` fixed.
 
 * Python int array check/conversion ensuring C++ compatibility added.
 
 * C/Python interfaces for computing prior value added.
 
-* STIR spect matrix added.
-
 * Zenodo citation file added.