[Feature] Pass messages from proxy to backend

[Prof-Bloodstone]

Proposed Feature Description:

Ability for backend plugins to react to player messages, when proxy version of CarbonChat is used

Proposed Feature Functionality:

Instead if denying the player messages on proxy level, they should be passed down to the backend.

At least having the proxy send the message just for "informational" purposes (i.e. MC->Discord bridge) would be a great improvement, but having some sort of (configurable?) interop with backend would be nice (i.e. let backend cancel the message) could also be useful.