[FEATURE-39] Add scripts to serve production build locally

[davorpa]

What does this PR do?

Add feature(s)

Description

This PR allows running the production-optimized build locally.

I know that we have npm start but is not the same. This script runs the app in developvement mode, not in production.

Adds the npm run serve script for such case, making use of the cross-env library to set PUBLIC_URL before building the project.

Useful to view/test the app locally before deploying to production npm run deploy.

Context

• Documentation: https://cra.link/deployment
• Feature requested in [BUGFIX-37] Relative urls with a harcoded contextPath #38 (comment)