Added sub-type exclusion note

Author: camrein

doc/analyzers/PH_S032.md

@@ -12,7 +12,7 @@ Encapsulate the exceptions in a task using `Task.FromException(...)`.
 ## Options
 
 ```ini
-# A white-space separated list of exception types to not report
+# A white-space separated list of exception types to not report. The sub-types of these types will be excluded too.
 # Format: <type-specifier1> <type-specifier2> ...
 dotnet_diagnostic.PH_S032.exclusions = System.ArgumentException System.NotImplementedException
 ```