MAINTAINERS: add myself as maintainer for the interface code to swresample & swscale in libavfilter

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

MAINTAINERS

@@ -292,11 +292,13 @@ Generic parts:
 
 Filters:
   af_amerge.c                           Nicolas George
+  af_aresample.c                        Michael Niedermayer
   af_astreamsync.c                      Nicolas George
   af_atempo.c                           Pavel Koshevoy
   af_pan.c                              Nicolas George
   vf_delogo.c                           Jean Delvare (CC <khali@linux-fr.org>)
   vf_drawbox.c/drawgrid                 Andrey Utkin
+  vf_scale.c                            Michael Niedermayer
   vf_yadif.c                            Michael Niedermayer
 
 Sources: