Documentation on handling `SendMessageError`

# Give us your feedback about our samples

## Which sample do you want to give feedback?
https://github.com/MicrosoftDocs/azure-docs/blob/main/articles/azure-web-pubsub/reference-client-sdk-javascript.md#4-send-messages-to-a-group

### The sample is not what you want?
In production, we have occasionally run into the following error:

Type: SendMessageError
Message: The connection is not connected.
File:
Stack: SendMessageError: The connection is not connected.
at aVn._sendMessageWithAckId @
at async aVn._sendToGroupAttempt @
at async aVn._operationExecuteWithRetry @
at async aVn.sendToGroup

What is the proper way to handle this error?

Should we be checking the connection status before calling sendAsync? In other words, track status via client.on('connected') and client.on('disconnected'). And in that case, while the status is "disconnected", we would need to store all attempted messages so they can be resent once the client has successfully connected? Or does this library do all of that for us already?

Start with the linked azure-web-pubsub JavaScript client sample at the “Send messages to a group” section. Verify how SendMessageError, connection events, retries, and message resending are handled, then document the supported behavior and recommended response to a disconnected client.

Written by the indexing model from the issue text.