Support `nilerc`

This is related to #72 and something I personally wish was included. I think it would be helpful to have a configuration file that nile can use to lookup information such as:

• cairo path
• contracts directory

For example, the OZ cairo-contracts repository contains the cairo contracts in the openzeppelin directory and so nile compile won’t compile them.

I’m also using the OZ contracts in my project and at the moment I can’t compile with nile because I can’t add the git submodule to the cairo path.

[martriay]

Being a JS developer forced into python because of Cairo I can confirm I don’t know how to use these files. That being said, I’m not sure how feasible it really is to move away from it, since Nile’s scripting API is already python. I don’t have a strong opinion, I guess we can just have a nile.toml?

[milancermak]

I don’t think having it in pyproject.toml is a good idea. It’s a file intended for python packages, it doesn’t have anything to do with Nile. I’ve noticed a lot of people coming to the StarkNet ecosystem (and using nile) have JS dev background and don’t have experience with python. Using a python specific config file would confuse them even further (that’s why I’d also rather not use a .py file either).