Allow cbor-raw compression/encoding when clients publish to the rosbridge server

[ssnover]

Both the ros1 and ros2 protocol specifications define a means for transporting messages encoded as cbor-raw. This appears to currently be used to allow subscribers to request that the rosbridge server send them data encoded in this format. However, there is no means for a publisher to encode data in this format.

My request here is to expand the specification to add an optional parameter to advertise, compression which allows specifying cbor-raw as a compression mechanism such that client publishers may send data with this encoding.

Fully happy to implement this myself, but I'm not sure if the ros1 version of this codebase is still released and/or maintained. Since the argument is optional, it wouldn't require a major version change of the protocol specification as the change would be backwards compatible.