Circle config

[abrahamsangha]

What's this PR do?

Provides a base CircleCi config that will enable junit xml test metadata, which is needed for the Heartbeat application

Where should the reviewer start?

your call

How should this be manually tested?

You could make these exact changes to your unejected create-react-app based app that is already registered correctly in Heartbeat and see if the build data flows into KPI

Any background context you want to provide?

no

New dependencies? What are they used for?

jest-junit to produce the junit xml

Screenshots (if appropriate)

What gif best describes how this PR makes you feel?