[keyserver] Create dc.sh script

Summary:
We're going to want Docker hosts to run this script instead of docker compose and docker-compose commands. More details on why it's necessary in D4211 and ENG-1230.

Making this a bash script instead of a yarn script so that Docker hosts don't need to install yarn in order to run it.

Depends on D4212

Test Plan: I tested this in concert with D4211

Reviewers: palys-swm, atul

Reviewed By: palys-swm

Subscribers: Adrian, yayabosh

Differential Revision: https://phabricator.ashoat.com/D4213