add declarative config to methods readme

Author: zeitlinger

instrumentation/methods/README.md

@@ -10,3 +10,34 @@ occurrences. The resulting data is automatically translated into OpenTelemetry t
 | `otel.instrumentation.methods.include` | String | None    | List of methods to include for tracing. For more information, see [Creating spans around methods with `otel.instrumentation.methods.include`][cs]. |
 
 [cs]: https://opentelemetry.io/docs/zero-code/java/agent/annotations/#creating-spans-around-methods-with-otelinstrumentationmethodsinclude
+
+# Declarative Configuration Example
+
+In addition to configuring method instrumentation via system properties, you can use declarative
+configuration files to specify which methods to trace. This approach allows for more flexible and
+maintainable instrumentation settings.
+      
+Below is an example of a declarative configuration YAML file that enables tracing for a specific
+method:
+
+```yaml
+file_format: "1.0-rc.1"
+instrumentation/development:
+  java:
+    methods:
+      include:
+        - class: io.opentelemetry.javaagent.instrumentation.methods.MethodTest$ConfigTracedCallable
+          methods:
+            - name: call
+              span_kind: SERVER
+```
+
+**Explanation:**
+
+- `class`: The fully qualified name of the class containing the method to be traced.
+- `methods`: A list of method configurations for the specified class.
+  - `name`: The name of the method to trace.
+  - `span_kind`: The kind of span to create (e.g., SERVER, CLIENT).
+
+This configuration will instruct the OpenTelemetry Java agent to create a span around the `call`
+method of the specified class, with the span kind set to SERVER.