update examples doc.

doc/source/examples.rst

@@ -3,8 +3,12 @@ Examples
 
 The examples can be downloaded from https://github.com/pymodbus-dev/pymodbus/tree/dev/examples
 
-Examples version 3.x
---------------------
+.. tip:: The examples needs to be run from within the examples directory, unless you modify them.
+    Most examples use helper.py and client_*.py or server_*.py. This is done to avoid maintaining the
+    same code in multiple files.
+
+Examples:
+---------
 
 These examples are considered essential usage examples, and are guaranteed to work,
 because they are tested automatilly with each dev branch commit using CI.