GPIO section needs updating for Pi 5

[LizUpton]

https://github.com/raspberrypi/documentation/blob/develop/documentation/asciidoc/computers/raspberry-pi/gpio-on-raspberry-pi.adoc needs material on Pi 5, and detail about chips later than 2835 adding to the section at the top.

(Nate, as discussed!)

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[aallan]

No so fast github bot.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.