$ sudo apt-get update
$ sudo apt-get install libjs-leaflet-markercluster 

libjs-leaflet-markercluster is installed in your system.

Make ensure the libjs-leaflet-markercluster package were installed using the commands given below,

$ sudo dpkg-query -l | grep libjs-leaflet-markercluster *

You will get with libjs-leaflet-markercluster package name, version, architecture and description in a table

libjs-leaflet-markercluster package basic information: