[Monitor] Update READMEs (Azure#38900)

Add info about aiohttp when using async clients.

Signed-off-by: Paul Van Eck <[email protected]>

sdk/monitor/azure-monitor-ingestion/README.md

@@ -64,6 +64,12 @@ credential = DefaultAzureCredential()
 logs_client = LogsIngestionClient(endpoint, credential)
 ```
 
+To use the asynchronous clients, you must also install an async transport, such as [aiohttp](https://pypi.org/project/aiohttp/).
+
+```sh
+pip install aiohttp
+```
+
 #### Configure clients for non-public Azure clouds
 
 By default, `LogsIngestionClient` is configured to connect to the public Azure cloud. To connect to non-public Azure clouds, some additional configuration is required. The appropriate scope for authentication must be provided using the `credential_scopes` keyword argument. The following example shows how to configure the client to connect to Azure US Government:

sdk/monitor/azure-monitor-query/README.md

@@ -67,6 +67,12 @@ async_metrics_query_client = MetricsQueryClient(credential)
 async_metrics_client = MetricsClient("https://<regional endpoint>", credential)
 ```
 
+To use the asynchronous clients, you must also install an async transport, such as [aiohttp](https://pypi.org/project/aiohttp/).
+
+```sh
+pip install aiohttp
+```
+
 #### Configure client for Azure sovereign cloud
 
 By default, all clients are configured to use the Azure public cloud. To use a sovereign cloud, provide the correct `endpoint` argument when using `LogsQueryClient` or `MetricsQueryClient`. For `MetricsClient`, provide the correct `audience` argument instead. For example: