Add two new functions to interface with DragonflyDB pub/sub system:
- fnc_subscribe.sqf: Subscribe to channels with CBA event routing
- fnc_publish.sqf: Publish messages to channels
These functions integrate with the existing pubSubHandler to route
messages through CBA's event system using 'global', 'local', 'server',
and 'remote' event types.
Both functions include proper input validation, error handling, and
detailed documentation with examples.
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