[docs] Include documentation on running your own self-hosted keyserver through aws

Summary: Initial documentation on setting up your own self-hosted keyserver through aws

Test Plan: Was able to, from a clean aws account, deploy a fresh running keyserver following only directions from the docs

Reviewers: varun, ashoat

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D13105