Textadept Discord RPC v0.3-alpha

Simplified the C side so it provides connection details like the username, error messages etc. directly and seperately to Lua instead of pre-processing them into strings. This again improves the flexibility of what can be done in Lua without recompiling. With any luck the C side of things can be left alone now and any improvements will only update the Lua code.

At this point I am going to take a break from this for a few days before I look at adding features like tracking errors and name edge cases and better reconnect behaviour. This should be good to go for most people.

Build should work on Windows and Linux. I am looking into options to try and build/test a macOS version, but no guarantees.

Thanks and Merry Christmas! 🎄