Add descriptions for steps that can show up in ui

# Summary

Add step description field that can add human readable descriptions about the step.

# Motivation

We make the ui available for others on our teams to view, but they do not necessarily have the full technical understanding of what the workflow is doing. It would be great if instead we could offer them a description of a step when they click on it to get a summary of what the step is doing.

# Proposal
Not sure, but I'd imagine the end result would be an additional field within templates.steps when designing a workflow.

No files, tests, or entry points are named. Start by locating the workflow template schema for templates.steps and the UI view shown when a step is selected; define how a human-readable description is stored and displayed, and verify that the selected step shows it in the summary.

Written by the indexing model from the issue text.