[chore] add pipx, brewfile, and yamllint automation

[adrielp]

Changes

Adds pipx as a python virtual environment manager to the local development workflow. Adds yamllint to the list of checks. Adds brew to install pipx.

Merge requirement checklist

• [x] CONTRIBUTING.md guidelines followed.
• [x] Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• [x] schema-next.yaml updated with changes to existing conventions.