L2SS-1114: Add some improvements in how to use the HDF file reader

Closes L2SS-1114

lofar_station_client/file_access/README.md

@@ -66,14 +66,9 @@ these attributes. Therefor `attribute` allows to specify another member in the c
 
 ## Read a HDF file
 
-A file can be read using the `Hdf5FileReader` class:
+A file can be read using `read_hdf5`:
 
 ```python
-with read_hdf5('file_name.h5') as f:
-    data = f.read(Data)
+with read_hdf5('file_name.h5', Data) as data:
+    a = data.first_attr
 ```
-
-It should always be used in a `with` block to make sure the HDF5 file handles are cleand up properly.
-
-Currently, the data object read from the file is only usable within the `with` block since the data is lazily loaded.
-If needed eager loading could be added in the future.