algo: Add comments to RICH unpacker.

algo/detectors/rich/Unpack.h

@@ -133,6 +133,13 @@ namespace cbm::algo::rich
       u64 cbmTimePacket = 0;
       u64 refTime       = 0;
 
+      // FIXME: Magic number, should be named.
+      //
+      // Comment from RICH expert (Martin Beyer):
+      //  > This number will also be valid for the Cbm Rich, 1 Rich backplane contains max. 12 DiRICHes.
+      //  > For the Cbm Rich the number of backplanes will be scaled
+      //  > up. Nevertheless it is very likely that fewer DiRiches(maybe not constant)
+      //  > per backplane are used in the day1 setup.
       double prevLastCh0ReTime[13];  // 12 DiRICHes chnl0 + 1 CTS chnl0
       double mbsCorr = 0.;