Improved Herocard droprate

This is a minor update that improves the drop-rate on hero cards. Herocards can be found in golden treasure chests, but the drop rate was pretty much :

- First drop in random level 4-9
- Second drop at least 5 rooms later, and maximum 10 rooms later.

It would skip special rooms like coin-rooms and arena-rooms, and the end result is that it could be very hard to encounter them ;)

New drop rate is:

- First drop in random level 2-6
- All subsequent drops are 4 levels between - ALWAYS.

So let's say first chest pops up in level 4, then it will be levels 4,8,12,16,20, etc.

One tip: these chests CAN be placed in secret/hidden rooms, AND also be smart about your level-skipping exits if you want to hunt for Herocards ;)

Good hunting!

OH, also want to tell you about the next Orangepixel game coming SOON:

https://store.steampowered.com/app/1290780/Residual/