Document firmware specifics and update for RP2040 based designs

[jonnew]

We need instructions on updating firmware for the rp2040-based controller. There should be difference sections in the Developer guide for Arudino based designs and the latest rp2040 design:

https://open-ephys.github.io/commutator-docs/coax-commutator/developer-guide/index.html

Specifically,

• How to update firmware (e.g. Enable double-tapping reset button to enter bootloader commutator-controller#37)
• How to use binary_info feature to change the target commutator turn_ratio
• etc.