Added: React typescript application to example plugin (OFBIZ-12789)

To demonstrate node/npm functionality available to all components, a
small typescript react web application has been integrated into the
example plugin.

See example/REAME-react for information about how this integration was
created.

The example react app also demonstrates calling the REST API. The screen renderer 
generates a JWT token to access the API embedded and stores it in a hidden field
on the page where it can be accessed by client-side javascript code.
28 files changed