Signed-off-by: Lukas Puehringer <lukas.puehringer@nyu.edu>

As 'repository_tool' and 'repository_lib' are being deprecated,
hash bin delegation interfaces are no longer available in this
implementation. The example code in this file demonstrates how to
easily implement those interfaces, and how to use them together
with the TUF metadata API, to perform hash bin delegation.

Note, the hash bin delegation logic in this example is largely
copied from repository_{lib, tool}, and modernized and simplified
for this purpose.

Signed-off-by: Lukas Puehringer <lukas.puehringer@nyu.edu>

Signed-off-by: Lukas Puehringer <lukas.puehringer@nyu.edu>

Tries to clarify the introductory text in the hash bin delegation
example.

Signed-off-by: Lukas Puehringer <lukas.puehringer@nyu.edu>