PIO example which loads a .pio file

[thejpster]

If you are working with the Pico SDK, you might have some PIO code written out in a .pio file. We should have an example of some Rust code that can load the .pio file at compile time.

[doraneko94]

Do you want to add this example to the examples in this repository? Or is it sufficient since it currently exists in rp_hal_boards?

[ithinuel]

IMHO, rp-hal-boards is good enough.

[jannic]

https://github.com/rp-rs/rp-hal-boards/blob/main/boards/rp-pico/examples/pico_pio_pwm.rs#L132 does exactly that. So I think this ticket can be closed?