Update README.md

Co-Authored-By: Jae Lim <jaelim@microsoft.com>

README.md

@@ -89,7 +89,7 @@ let parsedCorrelationVector = CorrelationVector.parse("vtul4NUsfs9Cl7mOf.1")
 ## Create new vector via extending existing vector
 
 ```swift
-// Initialize "vtul4NUsfs9Cl7mOf.1.0" correlation vector via extending
+// Initialize "vtul4NUsfs9Cl7mOf.1.0" correlation vector by extending an existing value
 let correlationVector = try CorrelationVector.extend("vtul4NUsfs9Cl7mOf.1")
 ```