feat: Single player hosting in WebGL using RPC

[BenHamrick]

Expose the ability to use RPC especially on WebGL to allow us to easily make a single player mode while still using netcode usually as a host.

Changelog

• Added: The ability to use RPC using a property in the Transport.
• Changed: Allowed the ability to host a game if using RPC in WebGL to allow us to easily create a single player mode.

Testing and Documentation

• No tests have been added.
• No documentation changes or additions were necessary.

[CodeSmile-0000011110110111]

@BenHamrick Where is the RPCNetworkInterface type defined? I tried to add this change but cannot find such a class in the entire codebase, not even in your fork, and not on the Internet at large.