[docs] Rewrite of onboarding section for Dev Containers

[winstonwumbo]

New Features

• Reworked installation instructions in README based on feedback from MICS meeting
  • Focus on Dev Container method
  • macOS/Linux experience generally smooth
  • Added section to highlight any Windows prereqs more significantly
    • For now: users need to manually update WSL 2 w/ either Microsoft Store or PowerShell
    • Docker automatically opens a prompt for this during its install, but feedback was that it's easy to miss., then the experience is the same as on macOS/Linux.
• Migrated all the alternative install options into CONTRIBUTING
  • Lessens the mental load for new student contributors: there's only one main option in the README
  • CONTRIBUTING is typically read by more experienced users, so that's where our flexible options live now

[vercel]

@winstonwumbo is attempting to deploy a commit to the HAXTheWeb Team on Vercel.

A member of the Team first needs to authorize it.