Play Framework

docs: correct browser support for WebSocket Extended CONNECT (PF-156)

The note added with PF-158 claimed Chrome does not implement RFC 8441. That was
wrong: Chrome Platform Status records WebSockets over HTTP/2 as enabled by
default since Chrome 91, and Chromium ships
net/websockets/websocket_http2_handshake_stream.cc in production. The "Intent to
Prototype" status I attributed to it belongs to Chrome's separate HTTP/3
WebSocket entry (RFC 9220), which no browser has shipped.

Replaces it with the distinction that actually matters operationally: Chrome and
Firefox use Extended CONNECT only when an h2 connection to the origin is already
open and advertised the setting — neither opens a fresh h2 connection just to
carry a WebSocket, so a wss:// call against a cold origin still goes out over
HTTP/1.1. Also records that Safari has not shipped RFC 8441, and that RFC 9220
has no browser implementation yet.

No code change; the implementation and its fallback behaviour were already
correct for every case described.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>