add vehicles arg to readme (#83)

* add vehcls arg to readme

* Update README.md

Co-authored-by: Kasia Kozlowska <36536946+KasiaKoz@users.noreply.github.com>

README.md

@@ -34,7 +34,7 @@ To run pre-baked scripts that use genet in a number of different scenarios you c
 
     docker run genet reproject_network.py -h
 
-    usage: reproject_network.py [-h] -n NETWORK [-s SCHEDULE] -cp
+    usage: reproject_network.py [-h] -n NETWORK [-s SCHEDULE] [-v VEHICLES] -cp
                                 CURRENT_PROJECTION -np NEW_PROJECTION
                                 [-p PROCESSES] -od OUTPUT_DIR
 
@@ -46,6 +46,8 @@ To run pre-baked scripts that use genet in a number of different scenarios you c
                             Location of the network.xml file
       -s SCHEDULE, --schedule SCHEDULE
                             Location of the schedule.xml file
+      -v VEHICLES, --vehicles VEHCILES
+      							  Location of the vehicles.xml file
       -cp CURRENT_PROJECTION, --current_projection CURRENT_PROJECTION
                             The projection network is currently in, eg.
                             "epsg:27700"