doc: Document segment_list_type

doc/muxers.texi

@@ -503,6 +503,12 @@ extension.
 Set segment duration to @var{t} seconds.
 @item segment_list @var{name}
 Generate also a listfile named @var{name}.
+@item segment_list_type @var{type}
+Select the listing format.
+@table @option
+@item @var{flat} use a simple flat list of entries.
+@item @var{hls} use a m3u8-like structure.
+@end table
 @item segment_list_size @var{size}
 Overwrite the listfile once it reaches @var{size} entries.
 @item segment_list_entry_prefix @var{prefix}