chore: add FAQS to README

[a-wallen]

Having an FAQ section would be nice so people don't file bugs against known issues.

This PR adds FAQs so that we can close the following:

closes https://github.com/imbushuo/mac-precision-touchpad/issues/503 closes https://github.com/imbushuo/mac-precision-touchpad/issues/493

Once this PR lands, those get automatically closed.

p.s. sorry that there's some whitespace formatting changes here, my formatted removed trailing whitespace in sections outside of the FAQs. I can undo those changes, but I think that it's better anyway.

[a-wallen]

cc @imbushuo this is a super simple review 👍