Adding line saying connectionString must have correct format.

Author: v-jbasden

articles/azure-monitor/app/javascript-sdk.md

@@ -122,6 +122,8 @@ To paste the connection string in your environment, follow these steps:
 
    1. Replace the placeholder `"YOUR_CONNECTION_STRING"` in the JavaScript code with your [connection string](./sdk-connection-string.md) copied to the clipboard.
 
+      The `connectionString` format must follow "InstrumentationKey=xxxx;....". If the string provided does not meet this format, the SDK load process fails.
+
       The connection string isn't considered a security token or key. For more information, see [Do new Azure regions require the use of connection strings?](./sdk-connection-string.md#do-new-azure-regions-require-the-use-of-connection-strings).
 
 ### (Optional) Add SDK configuration