📝 [MCH] Small improvement in documentation

Author: aphecetche

Detectors/MUON/MCH/Geometry/Transformer/README.md

@@ -7,7 +7,7 @@
 Here you will find functions to perform transformations on MCH geometry : local
 to global, global to local, and various (mis)alignement ones.
 
-# MCH Transformations in JSON format
+## MCH Transformations in JSON format
 
 Also available is a CLI utility to extract MCH transformations (rotations and
 translations) from a Root geometry file and export them in JSON format :
@@ -16,11 +16,21 @@ translations) from a Root geometry file and export them in JSON format :
 o2-mch-convert-geometry --geom o2sim_geometry.root > geom.json
 ```
 
-The JSON output can be manipulated (like any other json file) with e.g. [jq](https://stedolan.github.io/jq/)
+The JSON output is compact on purpose, to save some space (e.g. on github).
 
-For instance, to sort the output per detection element id :
+But as any JSON it can be manipulated further with e.g. [jq](https://stedolan.github.io/jq/)
+
+For instance you can pretty-print it :
+
+```shell
+cat output.json | jq .
+```
+
+Or sort the output per detection element id :
 
 ```shell
 cat output.json | jq '.alignables|=sort_by(.deid)'
 ```
 
+That last command being the one that was used to produce the example [ideal-geometry-o2.json](../Test/ideal-geometry-o2.json) file.
+