Provide contract interface to pyckel

[glyh]

Is your feature request related to a problem? Please describe.
It would be helpful if pyckel user can see some type annotations with nickel.

Describe the solution you'd like
Use nickel to generate some types for language servers like pyright.

[yannham]

Hello,

I'm not really that familiar with the Python ecosystem - would you have a simple example of a Nickel contract, and you would use it from the Python side if this ideal interface would exist? Just to get a glimpse of what it would look like in practice.