Function reduce

reduce<T, R>(
reducer: (accumulator: R, chunk: T) => SyncOrAsync<R>,
initialValue: R,
): TransformStream<T, R>
Create a TransformStream that reduces all values to a single value
Type Parameters
- T
- R
Parameters
- reducer: (accumulator: R, chunk: T) => SyncOrAsync<R>
  The reducer function to apply to each chunk
- initialValue: R
  The initial value
Returns TransformStream<T, R>
A TransformStream that emits the final reduced value when the stream closes
Example
```
// Sum all numbers in a stream
const stream = readable.pipeThrough(reduce((a, b) => a + b));
const [sum] = await toArray(stream); // Gets the single reduced value
```
- Defined in index.ts:363