fix(exports): define __all__ in msgraph/__init__.py and fix grammar in README

Author: hardikkaurani

README.md

@@ -77,7 +77,7 @@ scopes = ['https://graph.microsoft.com/.default']
 
 ### 2.3 Initialize a GraphServiceClient object
 
-You must create **GraphServiceClient** object to make requests against the service. To create a new instance of this class, you need to provide credentials and scopes, which can authenticate requests to Microsoft Graph.
+You must create a **GraphServiceClient** object to make requests against the service. To create a new instance of this class, you need to provide credentials and scopes, which can authenticate requests to Microsoft Graph.
 
 ```py
 # Example using async credentials and application access.

msgraph/__init__.py

@@ -6,3 +6,9 @@
 from .graph_service_client import GraphServiceClient
 
 __version__ = VERSION
+
+__all__ = [
+    "__version__",
+    "GraphRequestAdapter",
+    "GraphServiceClient",
+]