Function count

count<V>(): Sink<V, number>
Creates a sink counting the items of the feed.
Warning
- Exhaustive: every item is drawn before the sink resolves, so an infinite feed never completes.
- Streaming: no more than the running count is held in memory, whatever the size of the feed.
- Stateful: the count covers the items drawn, so a sink closing a nested or truncated feed sees those alone.
Type Parameters
- V
  The type of items in the feed
Returns Sink<V, number>
A sink resolving to the number of items the feed carried
Example
```
await pipe(
  (items([1, 2, 3, 4, 5]))
  (count())
);  // 5

await pipe(
  (items<number>([]))
  (count())
);  // 0
```
- Defined in sinks/count.ts:47