Task: Add README at project level

[mpjovanovich]

Task

Since this is more likely going to be a showcase than something others will adopt, the README should explain:

• Link to demo video (in docs folder)
• Pedagogical value and motivation: based on classroom experience; student frustration with "thrown into an editor" scenario; provides structured guardrails as programming novices begin their coding journey
• How to rig up the project
  • Needs to have a "turnkey" way to run the project in dev environment using Firebase Emulator. This will necessitate setting up the DB.
  • Database schema / infrastructure code.
  • Exercise template structure