Add a simple RTIC example

[dsvensson]

Add an example that transmits one packet, and another example that receives this packet using embedded-hal on for example the bluepill platform.

https://github.com/rtic-rs

[fmckeogh]

It's not using RTFM, but I have a simple Blinky example here.

I still have to tidy up and fix some of the transmitting functionality - the syntax in the example is not final.

[dsvensson]

and/or perhaps https://github.com/embassy-rs/embassy