reduce.concurrent

```coffeescript
Reducer = (any, T)=>Promise|any
Foldable = Iterable|AsyncIterable|{ reduce: Reducer=>any }|Object

reduce.concurrent(
data Foldable,
reducer (any, any)=>Promise|any,
result any,
) -> Promise|any

reduce.concurrent(
reducer (any, any)=>Promise|any,
result any,
)(data Foldable) -> Promise|any
```

Concurrent `reduce`. Reduce operation happens by order of asynchronous resolution and then the order of data argument.

```javascript
reduce.concurrent(
[1, 2, 3],
async (total, number) => {
await Promise(resolve => setTimeout(resolve, number))
return total + number
},
0,
).then(console.log) // 6
```

Look at the existing reduce implementation in the codebase to understand the current structure. The new function needs to handle concurrent asynchronous operations while preserving order based on resolution and data argument. Start by examining how the library manages async iterables and reducers. Write tests to verify the concurrent behavior as described in the example.

Scritto dal modello di indicizzazione a partire dal testo della issue.