* Add a Mercure protocol 1.0 broadcast driver

* Fix the default FrankenPHP Mercure JWT audience (#1)

* Wrap the built-in Mercure hub's failures in a BroadcastException

* Accept base64:-prefixed Mercure encryption keys and reject truncated publish expirations

* Document the JWK shape returned by the Mercure channel encrypter

* Link the RFCs and packages referenced by the Mercure docblocks

* Authorize Mercure channels individually and harden the cookie path

A denied channel is now flagged in the auth response instead of failing
the whole batch, presence payloads carry the user's broadcasting
identifier like the other drivers, secure-prefixed cookies over a plain
HTTP hub fail at driver resolution, and a cookie-domain mismatch points
at the public_url configuration.

* Narrow the Mercure broadcast docblock array types

* formatting

* formatting

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Co-authored-by: Jems <5523410+J3m5@users.noreply.github.com>
Co-authored-by: Taylor Otwell <taylor@laravel.com>