Merge branch 'clusterMultiplicity_updateREADME' into 'master'

Clustering4D/README: added new plot clusterMultiplicity

See merge request !160

src/modules/Clustering4D/README.md

@@ -24,6 +24,7 @@ For each detector the following plots are produced:
 * Cluster charge histogram
 * 2D cluster positions in global coordinates
 * Cluster times
+* Cluster multiplicity
 
 ### Usage
 ```toml