add stack.yaml

[juhp]

I managed to build with lts-22 - happy to contribute my little stack.yaml config.

(Also using hackage: stack --resolver lts-20 install hnix-store-core-0.6.1.0 hnix-store-remote-0.6.0.0 saltine hnix hashing)

(Would be nice to bump some deps to allow building with newer versions of course.)

[juhp]

Anyway let drop my stack.yaml here in case it is useful for anyone:

resolver: lts-22.44
extra-deps:
- hnix-store-core-0.6.1.0
- hnix-store-remote-0.6.0.0
- saltine-0.2.2.0
- hashing-0.1.1.0
- lens-family-th-0.5.3.2
- algebraic-graphs-0.6.1

[sorki]

The big deps update is being worked on #1112, hopefully landing soon^tm (after one more round of hnix-store releases I guess)