Update maintainer list

[skip ci]

libs/maintainers.txt

@@ -146,6 +146,7 @@ statechart            Andreas Huber <ahd6974-boostorg -at- yahoo.com>
 static_assert         John Maddock <john -at- johnmaddock.co.uk>
 static_string         Krystian Stasiowski <sdkrystian@gmail.com>, Vinnie Falco <vinnie.falco@gmail.com>
 stl_interfaces        Zach Laine <whatwasthataddress -at- gmail.com>
+system                Peter Dimov <pdimov -at- gmail.com>
 test                  Gennadiy Rozental <rogeeff -at- gmail.com>, Raffi Enficiaud <raffi.enficiaud -at- free.fr>
 thread                Vicente J. Botet Escriba <vicente.botet -at- wanadoo.fr>
 throw_exception       Emil Dotchevski <emil -at- revergestudios.com>, Peter Dimov <pdimov -at- gmail.com>