Add a Markdown Linter to Pipeline

Description

Adding a Markdown linter to the ironbank-pipeline pipeline

Purpose

Enforce consistency for pipeline documentation.

Plan

Research available options and select a md linter. Discuss and create a style guide/config for the selected tool.

For example markdownlint which has a VS Code plugin.

Possible Blockers/Challenges

Agreeing on a config for the selected tool.

Acceptance Criteria

Markdown lint job is enabled and pipeline passes job.