Clarify that both / and \ slashes are accepted in py -V:company/tag

Author: Jah-yee

Doc/using/windows.rst

@@ -162,7 +162,7 @@ omitted in cases where the tag refers to an official release and starts with
    $> py -V:3-arm64 ...
 
 Runtimes from other distributors may require the *company* to be included as
-well. This should be separated from the tag by a slash, and may be a prefix.
+well. This should be separated from the tag by a slash (either ``/`` or ``\\``, both are accepted on Windows), and may be a prefix.
 Specifying the company is optional when it is ``PythonCore``, and specifying the
 tag is optional (but not the slash) when you want the latest release from a
 specific company.