add example: Rust with axum framework

[abhinav-m22]

This new example will demonstrate how to integrate Polar using the Rust Axum web framework.

@rishi-raj-jain 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]

No worries, I’ll still give it a try