[keyserver] Dockerfile for Node keyserver
Summary:
With script dependencies in place, this diff completes the Dockerfile for the Node keyserver.
Depends on D3870
Test Plan: docker-compose up --build
Reviewers: palys-swm, jimpo
Reviewed By: palys-swm
Subscribers: Adrian, atul, karol-bisztyga, yayabosh
Differential Revision: https://phabricator.ashoat.com/D3871