docs: Rationalize wsjson buffer pooling and explain tradeoffs

I see that this library is using `sync.Pool` to pool buffers for wsjon sub-package. `sync.Pool` is suitable only for pooling objects of same size. If they are of different size, you have a problem: those buffers will just grow and grow never to shrink.

See https://github.com/golang/go/issues/23199 for more background.

Locate the wsjson sub-package and its sync.Pool buffer implementation, then read the linked Go issue about pooling objects of different sizes. Determine the current buffer-size behavior and document the tradeoffs of the available pooling approach. Done means the pooling strategy is rationalized and its limitations are explained.

Rédigé par le modèle d'indexation à partir du texte de l'issue.