doc: update instructions to build for G0B1RE

We are changing the microcontroller platform to an STM32G0B1RE, so
update the documentation to reflect the build commands, information
on how to flash, and the connections to the evaluation board.

BUG=b:241105740
TEST=Follow instructions in README.md to build and flash. Use jumper
wires to connect the eval boards, and experiment with adjusting the
output voltage.

Change-Id: Ia8080bee202fff97f8a199a5c945916e19400857
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/electric-eel/+/3814045
Tested-by: Paul Fagerburg <pfagerburg@chromium.org>
Reviewed-by: Brian Nemec <bnemec@google.com>
7 files changed