How does `createSlice` work and what does it return?

createSlice accepts a configuration object and returns an object containing:

• reducer: The slice reducer function
• actions: Object with action creators for each reducer
• name: The slice name
• getInitialState: Function returning initial state

const counterSlice = createSlice({
  name: 'counter',
  initialState: { value: 0 },
  reducers: {
    increment: (state) => {
      state.value += 1; // Immer makes this safe
    },
    incrementByAmount: (state, action) => {
      state.value += action.payload;
    }
  }
});
// Returns: { reducer, actions: { increment, incrementByAmount } }