Document PowerPak workaround

README.md

@@ -68,6 +68,8 @@ A link to the BPS can be found on the [releases page](https://github.com/kirjava
 
 The BPS produces a file with its header specifying MMC1 with fixed PRG (mapper 1:5), but it also works when specified as CNROM with bus conflicts (mapper 3:2).
 
+If you are using a PowerPak, you will need to install an [alternate N.MAP loader](https://forums.nesdev.org/viewtopic.php?p=283943#p283943) so its header check passes.
+
 ## Trainers
 
 Some trainers have additional configuration values; use left and right in the main menu to change them.