docs(api): clarify ilgs span whitespace coverage

Author: umarbutler

openapi.yaml

@@ -3374,7 +3374,9 @@ components:
         be duplicated.
 
 
-        A span cannot be empty and will never start or end at whitespace.
+        A span cannot be empty and will never start or end at whitespace (though a
+        span''s `end` index, being an exclusive index, may obviosuly land on a whitespace
+        character).
 
 
         Note that, when using programming languages other than Python (which uses