GitHub Workflow: Source Deno Version

[WilliamBergamin]

Source Deno version in GitHub Actions

Currently the GitHub Actions hard codes the deno-version value, Ideally we want the the deno-version value to be sourced dynamically from https://api.slack.com/slackcli/metadata.json 🔗

It is possible to set environment variable in a step this could be a potential solution to fetch, parse and set the deno-version

Context: #5 this comment