`load.py` and `schema.py` examples from cli

[francesco086]

As a dac package producer
I would like to see example implementations of load.py and schema.py
so that I can understand what I am expected to implement

Open question: is this sufficient? Perhaps some documentation is also needed?

[sebastianangst]

There is an example here, but I think it is too hidden. So user documentation or even README (in case you want to add more information there) would be good places to add examples.