feat: Markdown standard for client docs

[mthomps4]

Changes

• Adds .markdownlint.json
  • Adds default set of rules
• Adds settings and extension recommend
• Updates root Readme to adhere to new rules

Why

I don't really care which rules get thrown into the .markdownlint file. My goal here is to have something* to start with. I personally add this to every client project when creating .md docs for handoff.