Write a SpacetimeDB backend module in TypeScript that defines a table with optional (nullable) fields and a reducer that inserts rows with and without optional values.

TABLES
- player
  - Fields:
    - id: number (u64, primary key, autoInc)
    - name: string
    - nickname: optional string (use t.option(t.string()))
    - highScore: optional number (use t.option(t.u32()))

REDUCERS
- create_player(ctx, { name: string, nickname: optional string, highScore: optional number (u32) })
  - Insert a player row, passing through the optional fields as-is
  - Use id: 0n for autoInc
