Move code from README into a basic example

Author: djc

README.md

@@ -54,55 +54,7 @@ The crate provides the following types:
 
 [msrv]: #supported-rust-versions
 
-## Examples
-
-### Basic Usage
-
-```rust
-use opentelemetry::trace::TracerProvider as _;
-use opentelemetry_sdk::trace::TracerProvider;
-use opentelemetry_stdout as stdout;
-use tracing::{error, span};
-use tracing_subscriber::layer::SubscriberExt;
-use tracing_subscriber::Registry;
-
-fn main() {
-    // Create a new OpenTelemetry trace pipeline that prints to stdout
-    let provider = TracerProvider::builder()
-        .with_simple_exporter(stdout::SpanExporter::default())
-        .build();
-    let tracer = provider.tracer("readme_example");
-
-    // Create a tracing layer with the configured tracer
-    let telemetry = tracing_opentelemetry::layer().with_tracer(tracer);
-
-    // Use the tracing subscriber `Registry`, or any other subscriber
-    // that impls `LookupSpan`
-    let subscriber = Registry::default().with(telemetry);
-
-    // Trace executed code
-    tracing::subscriber::with_default(subscriber, || {
-        // Spans will be sent to the configured OpenTelemetry exporter
-        let root = span!(tracing::Level::TRACE, "app_start", work_units = 2);
-        let _enter = root.enter();
-
-        error!("This event will be logged in the root span.");
-    });
-}
-```
-
-`Cargo.toml`
-```toml
-[dependencies]
-opentelemetry = "0.21"
-opentelemetry_sdk = "0.21"
-opentelemetry-stdout = { version = "0.2.0", features = ["trace"] }
-tracing = "0.1"
-tracing-opentelemetry = "0.22"
-tracing-subscriber = "0.3"
-```
-
-### Visualization example
+## Visualizing traces with Jaeger
 
 ```console
 # Run a supported collector like jaeger in the background

examples/basic.rs

@@ -0,0 +1,30 @@
+use opentelemetry::trace::TracerProvider as _;
+use opentelemetry_sdk::trace::TracerProvider;
+use opentelemetry_stdout as stdout;
+use tracing::{error, span};
+use tracing_subscriber::layer::SubscriberExt;
+use tracing_subscriber::Registry;
+
+fn main() {
+    // Create a new OpenTelemetry trace pipeline that prints to stdout
+    let provider = TracerProvider::builder()
+        .with_simple_exporter(stdout::SpanExporter::default())
+        .build();
+    let tracer = provider.tracer("readme_example");
+
+    // Create a tracing layer with the configured tracer
+    let telemetry = tracing_opentelemetry::layer().with_tracer(tracer);
+
+    // Use the tracing subscriber `Registry`, or any other subscriber
+    // that impls `LookupSpan`
+    let subscriber = Registry::default().with(telemetry);
+
+    // Trace executed code
+    tracing::subscriber::with_default(subscriber, || {
+        // Spans will be sent to the configured OpenTelemetry exporter
+        let root = span!(tracing::Level::TRACE, "app_start", work_units = 2);
+        let _enter = root.enter();
+
+        error!("This event will be logged in the root span.");
+    });
+}