Web site docker image points to service on localhost

[qtomlinson]

Expected:
Should be able to use web site deployment to see definition at https://dev.clearlydefined.io/definitions/maven/mavencentral/org.osgi/osgi.annotation/8.1.0

Actual
empty page

Cause:
The web site communicates with service at localhost:4000

The Dockerfile for website contains two build args. These need to be set during build time. The default value for REACT_APP_SERVER is localhost:4000 and is currently used. The specific values are documented in Azure pipeline.