Update README.md

README.md

 # ippidb-web
 
-This repository contains the django web application that manages the iPPI-DB
-database. 
+This repository contains the django web application that manages the iPPI-DB database. 
+
+The pre-prod branch (i.e: master) is served at https://ippidb.dev.pasteur.cloud/.
 
 ## run flake8 before commit
 From the root of the project:
@@ -51,4 +52,4 @@ date
 # 5 minutes
 gzip -d -c ippisite/db-django-4.0.sql.gz  | kubectl exec --stdin --tty $POD -- psql
 date
-```
\ No newline at end of file
+```