docs: Readme/Usage org idea

[stern-shawn]

Docs

• Making a pass at cleaning up the examples in the current README, bringing them together under the existing usage.md file, and organizing things
• Fix broken syntax highlighting in usage.md
• Clarifying provider arguments
• General markdown linting

This is just an idea. I think usage.md is a pretty old file, and if it's not in use I can probably just port the new table of contents, etc back into the README if you feel that's more appropriate.

[childish-sambino]

LGTM