add example: java with spring boot framework

[abhinav-m22]

This new example will demonstrate how to integrate polar using spring boot and polar's REST API.

I’d like to take this on and contribute. Please assign it to me if that works!

[rishi-raj-jain]

Unfortunately, there's no bounty for this. Would you still want to proceed?

[abhinav-m22]

Yes, I’ll give it a try