Migrate to latest Tailwind setup for CRA

[pattruong]

Tasks

May want to do this right before final release so that development branches aren't interrupted

• migrate to canonical setup for CRA (https://tailwindcss.com/docs/guides/create-react-app)

Notes

• minimizes custom setup that are mixed from easily 5+ sources on tailwind setup
• can easily update to standard postcss & tailwindcss dependency in the future -- currently have to use compatibility version
• Track support for PostCSS 8 on CRA
  • PostCSS 8 facebook/create-react-app#9664
  • Update to PostCSS 8 facebook/create-react-app#9716
  • Update postcss packages facebook/create-react-app#10003
  • Revert "Update postcss packages" facebook/create-react-app#10216

[pattruong]

Monitoring build of #152 for successful deploy