Small completionism improvement — Demons Happened Steam update #234511

Some players were rightly confused by the optional tags and the amount of crystals in the game, here's something to make completionism more straightforward. Replaced the skull tag with a dead demon tag. It should be clearer now that you get that by killing every demon in the room. Made the demon tag red instead of blue. Red is clearly associated with the enemies, it makes more sense. Removed the heart tag. The game is already challenging as it is, and while it's nice to keep track of the levels where you managed not to get hit a single time the information wasn't used anywhere, and adding an achievement for finishing the game untouched would just make everyone salty. Get hit at your heart's content! Added easy crystals to normal rooms that were missing one. Just for consistency, they don't add challenge but it was confusing to find some random levels without a gem.