fix(docs): doc improvements (#359)

Author: stainless-app[bot]

README.md

@@ -315,7 +315,7 @@ The context manager is required so that the response will reliably be closed.
 
 ### Making custom/undocumented requests
 
-This library is typed for convenient access the documented API.
+This library is typed for convenient access to the documented API.
 
 If you need to access undocumented endpoints, params, or response properties, the library can still be used.