doc: update readme example

Author: cboudereau

README.md

@@ -33,5 +33,5 @@ services:
 
 ## isql demo
 ```bash
-echo -e "select top 10 * from <YourTable>\ngo" | isql -Usa -P${SA_PASSWORD} -D${DATABASE}
+. /opt/sap/SYBASE.sh && echo -e "select top 10 * from <YourTable>\ngo" | isql -Usa -P${SA_PASSWORD} -D${DATABASE}
 ```