chore: set up npm workspaces with shared package

[alecananian]

PR Checklist

• Includes changes to desk files
• Describes how you tested the PR locally (test ship vs livenet)
• If a new feature, includes automated tests
• Comments added anywhere logic may be confusing without context

Changes

• Updates repository to use npm workspaces
• Creates shared package at packages/shared with sample shared type to start
• Updates the web UI's group state manager to use the example shared type
• Moves Spill app into monorepo architecture at apps/spill

Tested with my livenet ship:

1. Delete all existing node_modules folders in your repo: rm -rf ./**/node_modules
2. Install dependencies at the root level: npm i
3. Navigate to the spill app cd apps/spill and start the Metro packager: npm start
4. Plug in your device or start the iOS simulator and run spill: npm run ios

No changes were made to the way the web UI is run for now

[linear]

LAND-1498 Code management: RN + web scaffolding

[alecananian]

No longer relevant; will reopen later with a different app package