examples.boilerplate: modify to use port groups

[isabelburgos]

Follow up to #599 - replacement of pads with ports. Added an "example" pin to demonstrate get_port_groups syntax, although this feels clunky compared to the previous boilerplate which had no pins.

[isabelburgos]

This is an idea for an expanded boilerplate applet that shows how to use in and out fifos and ports; feel free to ignore and we can go back to the previous commit and just use "data" instead of "example".