demux_lavf: detect ico as images

demux/demux_lavf.c

@@ -671,6 +671,7 @@ static bool is_image(AVStream *st, bool attached_picture, const AVInputFormat *a
         bstr_endswith0(bstr0(avif->name), "_pipe") ||
         strcmp(avif->name, "alias_pix") == 0 ||
         strcmp(avif->name, "gif") == 0 ||
+        strcmp(avif->name, "ico") == 0 ||
         strcmp(avif->name, "image2pipe") == 0 ||
         (st->codecpar->codec_id == AV_CODEC_ID_AV1 && st->nb_frames == 1)
     );