feat: add HTTP invocation example

[Vijay-K-2003]

Description

This PR adds a new example demonstrating how to invoke an HTTP service using Dapr's HTTP proxying capabilities within the Rust SDK ecosystem.

Specifically, it includes:

• invoke-http-client: Uses reqwest to dispatch a request to the local Dapr sidecar port (DAPR_HTTP_PORT), setting the dapr-app-id header to seamlessly route the request via Dapr.
• invoke-http-server: Implements a minimal Tokio TCP server acting as the invocation target mapping to 127.0.0.1:8080, removing the need for external HTTP server frameworks.
• Dapr configuration: Added dapr.yaml to according to other examples allowing the entire example to be tested easily with a single dapr run -f . command.
• Updated examples/Cargo.toml and authored a local README.md to guide users on how to run the example.

Issue reference

This PR will close #243

Checklist

• Code compiles correctly
• Created/updated tests
• Extended the documentation