TST: update path consistency, adjust documentation

[tangkong]

Description

• fixes a quick bug that manifests depending on where you run pytest.
  • pytest is meant to be run from the repository root, but can also run from inside the test folder.
  • test_create_arg expected pytest to be invoked from the repository root, and would fail if run from elsewhere
  • we should still advocate for running from the repository root, but it doesn't hurt to be less fragile
• includes an ascii map for the mock beamline defined in happi_db.json.
  • Included this in the conf.yaml because json doesn't support comments
• Fixes some stray formatting errors in the github.io docs

Motivation and Context

Uncovered while helping Jane debug some unit tests.

How Has This Been Tested?

By ensuring the test suite still works

Where Has This Been Documented?

This PR

Pre-merge checklist

• Code works interactively (a real hutch config file can be loaded)
• Code contains descriptive docstrings, including context and API
• New/changed functions and methods are covered in the test suite where possible
• Test suite passes locally
• Test suite passes on GitHub Actions
• Ran docs/pre-release-notes.sh and created a pre-release documentation page
• Pre-release docs include context, functional descriptions, and contributors as appropriate

[janeliu-slac]

Looks good to me.