Update README.md

Author: ue71603

examples/functions/drt/README.md

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-# DRT examples and explanations
+# DRT examples and explanations
+We expanded for NeTEx 2.1 DRT in serious manner.
+
+## Updates in NeTEX 2.1
+- `FlexibleLine` is folden into `Line`. Be aware that an area-oriented services is also a "line".
+- There can now exist multiple `ServiceBookingArrangement` and related stuff in a `mobilityService`.
+- There can now be also (multiple) `ServiceBookingArrangement` in a `Line`.
+- `BookingNote` is now also an object that can be referenced and translated with `AlternativeText`. **TODO**
+- `serviceBookingArrangements` can now accept all other elements to describe the services:
+  - `ServiceBookingArrangement`: How to book
+  - `ServiceCompetitiveCondition`: What to do and what not
+  - `ServiceEligibilityCondition`: Who can use the service.
+- The interaction of such serviceBookingArrangements is additive. Eg. all elements are within their group connected by OR. E.g. you are a senior or a child you can use the service. Be aware that this MAY result in the need to split a service to do it.
+
+## Examples 
+
+### Switzerland
+
+### ENTUR