vlc-video: Use case insensitive compare for valid extension check

It's possible for files to have some/all characters uppercase.

Fixes #3562

plugins/vlc-video/vlc-video-source.c

@@ -554,7 +554,7 @@ static bool valid_extension(const char *ext)
 		else
 			dstr_copy(&test, b);
 
-		if (dstr_cmp(&test, ext) == 0) {
+		if (dstr_cmpi(&test, ext) == 0) {
 			valid = true;
 			break;
 		}