Update maintainer list.

libs/maintainers.txt

@@ -30,6 +30,7 @@ config                John Maddock <john -at- johnmaddock.co.uk>
 container             Ion Gaztanaga <igaztanaga -at- gmail.com>
 context               Oliver Kowalke <oliver.kowalke -at- gmail.com>
 conversion            Antony Polukhin <antoshkka -at- gmail.com>
+convert               Vladimir Batov <vbmail247 -at- gmail.com>
 core                  Peter Dimov <pdimov -at- pdimov.com>, Glen Fernandes <glenfe -at- live.com>, Andrey Semashev <andrey.semashev -at- gmail.com>
 coroutine             Oliver Kowalke <oliver.kowalke -at- gmail.com>
 crc                   Daryle Walker <darylew -at- hotmail.com>