Rewrite readme

extras/heavy_em_n3lo/README.md

@@ -1,7 +1,16 @@
 In order to compute all the N3LO grids run
 ```
 python produce_grids.py
+
 cores=4
 order=3
-for nf in 3 4 5; do for kind in 2 L ; do for channel in g q ; do python yad_grids.py $nf $cores $kind $channel $order gm ; done ; done ; done
+
+for nf in 3 4 5; do
+    for kind in 2 L; do
+        for channel in g q; do
+            python yad_grids.py $nf $cores $kind $channel $order gm;
+        done
+    done
+done
+
 ```