New repo request: phosphor-power-monitor

[Brandon Wyman]

Hello Brad,

Could you please create a new repository called phosphor-power-monitor?

I am proposing that this new repository be used for the single power
supply monitoring application, design under review here:
https://gerrit.openbmc-project.xyz/c/openbmc/docs/+/23038

This repository may get used for some other future applications
related to power monitoring.