avfilter/vf_swaprect: add timeline support

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavfilter/vf_swaprect.c

@@ -252,4 +252,5 @@ AVFilter ff_vf_swaprect = {
     .uninit        = uninit,
     .inputs        = inputs,
     .outputs       = outputs,
+    .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,
 };