Improve documentation around using reqwest with this library

Author: davidsteiner

README.md

@@ -12,7 +12,7 @@ They don't have similar support for Rust. However, they do support the
 This crate contains the necessary glue to bridge the gap between OpenTelemetry
 and Datadog.
 
-# Features
+# Further Information and Rationale
 ## Tracing
 For traces, the official Datadog agent
 [can ingest OTel trace data](https://docs.datadoghq.com/opentelemetry/)
@@ -21,7 +21,7 @@ via either HTTP or gRPC. More information on this can be found here:
 https://docs.datadoghq.com/opentelemetry/otlp_ingest_in_the_agent/?tab=docker
 
 OpenTelemetry has an official Rust crate with extensions for major 
-formats/providers. This includes a datadog exporter. We have found
+formats/providers. This includes a Datadog exporter. We have found
 this exporter to be less reliable than the standard OTel exporter
 sending data to the OTel endpoint of the Datadog agent, though.
 
@@ -39,14 +39,39 @@ transform the trace ID to the Datadog native format.
 
 ## Propagation
 The Python library takes care of propagation of the trace context automatically.
-Unfortunately, we need to do this manually in Rust. There are many protocols and
-corresponding libraries we could support, but the main one is HTTP requests.
+Unfortunately, we need to do this manually in Rust.
 
 In Rust, `reqwest` is the most commonly used HTTP client crate. We provide a 
 `reqwest` middleware that injects the necessary headers using the Datadog native
 propagation standard (common alternatives would be Jaeger and B3, more on this:
 https://opentelemetry.io/docs/reference/specification/context/api-propagators/#propagators-distribution).
 
+This crate does not provide any additional support, but we recommend using
+the [reqwest-middleware](https://crates.io/crates/reqwest-middleware) crate
+to inject the necessary headers. If you set the global propagator using
+`ddtrace`, it will work out of the box.
+
+```rust
+use ddtrace::set_global_propagator;
+use reqwest_middleware::{ClientBuilder, ClientWithMiddleware};
+use reqwest_tracing::TracingMiddleware;
+
+#[tokio::main]
+async fn main() {
+    set_global_propagator();
+    client = get_http_client();
+    
+    // configure tracing, setup your app and inject the client
+}
+
+fn get_http_client() -> ClientWithMiddleware {
+    ClientBuilder::new(reqwest::Client::new())
+        .with(TracingMiddleware::default())
+        .build()
+}
+```
+
+
 ## Axum Support
 The trace context propagated from other services needs to be extracted and injected
 into the propagator. For `axum`, our choice of HTTP API framework, a third-party crate