Add slick

[ChrisPenner]

Checklist:

• Meaningful commit message, eg add my-cool-package (please not mention build-constraints.yml)

• At least 30 minutes have passed since uploading to Hackage

• On your own machine, you have successfully run the following command (find verify-package in the root of this repo):

  ./verify-package $package # or $package-$version
  

The script runs virtually the following commands in a clean directory:

  stack unpack $package-$version # `-$version` is optional
  cd $package-$version
  rm -f stack.yaml && stack init --resolver nightly --ignore-subdirs
  stack build --resolver nightly --haddock --test --bench --no-run-benchmarks

[alexeyzab]

Thanks!