Support stack

[chshersh]

Blocked by #38

stack is a common Haskell build tool. Some developers still prefer stack and use only stack for their Haskell development. Adding Stack support would enable contributors who use only stack and allow Iris to be added to Stackage later,

To add stack, one need to:

1. Add stack.yaml using the latest nightly resolver (so Iris can be added to Stackage later).
2. Add a CI job for building Iris with stack. Refer to Dead Simple Cross Platform GitHub Actions for Haskell blog post.
3. Fix all compilation and CI errors.