Update Mint/Ubuntu FAQs to mention mic low volume problem

[RayBB]

It's mention in the readme here but it would be great if we mentioned it on the FAQs page here and linked to the fix here.

Even better, if we had that fix automatically run as part of the install process but for now just updating the docs would be good.

I faced this issue myself and jumping between the docs in multiple places was a hassle that we can fix easily.

[AdityaGarg8]

The T2-Mint readme hasn't been updated for years since we have a whole wiki now. You can open a PR for the wiki though.