Add Snakemake workflow tests to Funnel

[lbeckman314]

Overview

Adding Snakemake tests to Funnel would allow for increased interoperability with existing workflows. Ideally the tests would be automated and be able to run in Github Actions à la the nf-canay test suite used for Nextflow

See Pull Request #761 for an example of integrating this into Funnel's testing.

It might be worth considering the snakemake-github-action as part of this effort.