Icon fix

• Refactored to utilize a CAPI callback. The code is so short and clean now!!
  
• Extended Item Descriptions compatibility
  
• Interaction with Mom's Box: fires will increase drop odds to 75%. That's HALF the odds of NOT getting a drop.

Some comments in main.lua were inaccurate...now they're not ._.

Changed ember drop odds to 1%, in response to many complains that ember was appearing too often.

In order to make this happen, I had to switch from ints to floats for RNG, since the the actual number I'm rolling for is 1.18%... It's complicated.

Ember now operates within the 85% probability window of fires NOT DROPPING THINGS. Previously, I deleted all natural fire drops so I could strictly enforce my own probabilites, but that seemed like bad practice. Now it should play a little nicer with other fireplace mods.

Gameplay-wise, you won't even know anything's changed!

Ember is now compatible with ALL types of hearts and coins! And I didn't even need the new callbacks. Thanks to a tip from spider853, I figured out how to make the game spawn random collectibles.

Just cleaned up the code a little. There shouldn't be any differences gameplay-wise.

- Added art by PJJLegend. Thanks, PJ! (I didn't pay him)
- Original art and one other submission can be found in the files, if you're into that
- Ember now only spawns once per run from a fireplace (You can still get it from Mom's Box, random drops, etc). Hope it spawns somwhere you can reach!!