add teensy demo example

[SquadQuiz]

@RobTillaart
Refer to #53

I would like to create a pull request to add demo example teensy.

Thanks

[RobTillaart]

@SquadQuiz
Can you tell me what is specific teensy in the example?
It looks just like a copy of AS5600_demo.ino and if so it adds no value for the users.

[SquadQuiz]

@RobTillaart
Please accept my apologies that I',m overlooking on AS5600_demo.ino sketch.
So no need to add this sketch to your repo.

[RobTillaart]

No need to apologize, such things can happen.
Anyway thanks for the intention and your effort!