Are there any plans to implement prepared writes?

I'm currently working on a websocket-based broadcasting server and would be more then happy to use this great library, but there is no prepared writes functionality, like in some other websocket libraries (e.g. [gorilla/websocket](https://github.com/gorilla/websocket) and [lxzan/gws](https://github.com/lxzan/gws/tree/main)). This would help a lot to optimize the broadcasting of identical messages. Are there any plans to implement this feature in some way (or accept PRs that implements it)?

I'm not sure how the API should look like, but it would be cool to have something similar.
```Go
var connections []*websocket.Conn

// Create prepared message without frames generation.
pm := websocket.PrepareMessage(websocket.MessageText, []byte("hello"))
defer pm.Close()

for _, c := range connections {
// Lazily initialize frame buffer for "pm" and reuse it for other connections.
// For each set of compression settings (mode and threshold), there will be separate pre-initialized frame
// buffers, so if some connections don't have compression enabled and some do have, then two types of
// frame buffers will be initialized for each of them.
if err := c.WritePrepared(ctx, pm); err != nil {
log.Printf("failed to write prepared message: %v\n", err)
}
}
````

Start by reviewing the library's existing websocket.Conn write API and the proposed PrepareMessage and WritePrepared entry points, then compare the cited gorilla/websocket and lxzan/gws behavior. Establish the API, compression interactions, and message lifecycle before implementation; done means an agreed design that supports reuse for identical broadcasts.

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