update readme to include Azure SDK support (#37606)

* update readme to include Azure SDK support

* changelog

* fix md error

sdk/monitor/Azure.Monitor.OpenTelemetry.AspNetCore/CHANGELOG.md

@@ -4,11 +4,10 @@
 
 ### Features Added
 
-* Added Azure.* activity sources.
-  Users will need to enable the collection by turning on the feature by following one of the ways listed in
-  [Introducing experimental OpenTelemetry support in the Azure SDK for .NET](https://devblogs.microsoft.com/azure-sdk/introducing-experimental-opentelemetry-support-in-the-azure-sdk-for-net/).
+* Added instrumentation support for Azure SDKs.
+  See [Enable Azure SDK Instrumentation](https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/monitor/Azure.Monitor.OpenTelemetry.AspNetCore/README.md#enable-azure-sdk-instrumentation) for details.
   ([#37505](https://github.com/Azure/azure-sdk-for-net/pull/37505))
-* Added `SamplingRatio` property to customize the sampling rate in Azure Monitor Exporter.
+* Added `SamplingRatio` property to customize the sampling rate in Azure Monitor Exporter. **Note**: This package no longer takes dependency on [OpenTelemetry.Extensions.AzureMonitor](https://www.nuget.org/packages/OpenTelemetry.Extensions.AzureMonitor)
   ([#36972](https://github.com/Azure/azure-sdk-for-net/pull/36972))
 
 ### Other Changes

sdk/monitor/Azure.Monitor.OpenTelemetry.AspNetCore/README.md

@@ -180,6 +180,24 @@ builder.Services.AddOpenTelemetry().UseAzureMonitor();
 builder.Services.ConfigureOpenTelemetryTracerProvider((sp, builder) => builder.AddGrpcClientInstrumentation());
 ```
 
+#### Enable Azure SDK Instrumentation
+
+Azure SDK instrumentation is supported under the experimental feature flag which can be enabled using one of the following ways:
+
+* Set the `AZURE_EXPERIMENTAL_ENABLE_ACTIVITY_SOURCE` environment variable to `true`.
+
+* Set the Azure.Experimental.EnableActivitySource context switch to true in your app’s code:
+    ```csharp
+    AppContext.SetSwitch("Azure.Experimental.EnableActivitySource", true);
+    ```
+
+* Add the RuntimeHostConfigurationOption setting to your project file:
+    ```csharp
+    <ItemGroup>
+        <RuntimeHostConfigurationOption Include="Azure.Experimental.EnableActivitySource" Value="true" />
+    </ItemGroup>
+    ```
+
 #### Adding Another Exporter
 
 Azure Monitor Distro uses the Azure Monitor exporter to send data to Application Insights. However, if you need to send data to other services, including Application Insights, you can add another exporter. For example, to add the Console exporter, you can install the [OpenTelemetry.Exporter.Console](https://www.nuget.org/packages/OpenTelemetry.Exporter.Console) package and use the following code:
@@ -206,7 +224,6 @@ environmental variables:
 | `OTEL_RESOURCE_ATTRIBUTES` | Key-value pairs to be used as resource attributes. See the [Resource SDK specification](https://github.com/open-telemetry/opentelemetry-specification/blob/v1.5.0/specification/resource/sdk.md#specifying-resource-information-via-an-environment-variable) for more details. |
 | `OTEL_SERVICE_NAME`        | Sets the value of the `service.name` resource attribute. If `service.name` is also provided in `OTEL_RESOURCE_ATTRIBUTES`, then `OTEL_SERVICE_NAME` takes precedence. |
 
-
 ## Key concepts
 
 The Azure Monitor Distro is a distribution package which enables users to send telemetry data to Azure Monitor. It includes the .NET OpenTelemetry SDK and instrumentation libraries for [ASP.NET Core](https://www.nuget.org/packages/OpenTelemetry.Instrumentation.AspNetCore/), [HttpClient](https://www.nuget.org/packages/OpenTelemetry.Instrumentation.Http/), and [SQLClient](https://www.nuget.org/packages/OpenTelemetry.Instrumentation.SqlClient).