Initial implementation with useRacerState and renderReactComponent

[ericyhwang]

Repo setup:

• TypeScript project, targeting ES2020 and CommonJS module format
• Vitest test runner, ESLint + Prettier for linting
• GitHub Actions for CI

Two initial functions:

• useRacerState, which adds a React component state variable that's synchronized with the data at a specific Racer model path
• renderReactComponent, which renders a React component inside a Derby component, with appropriate cleanup hooks