Mobs Enhancement Addon V0.2.0 - Scaling Difficulty

-Fixed an issue where zombies keep breaking block when the block is replaced in creative mode.
-Decreased skeletons' base max health from 16 to 12.
-Increased creepers' base fuse time from 1s to 1.25s.
-Changed zombies to transform into a skeleton with half its max health when die of sunlight.
-Changed skeletons to no longer burn under sunlight.
-Added world difficulty level that increases on the first nether portal construction, the first wither summoning, and the first ender portal activation, which determines hostile mobs' max health and several other attributes and behaviors, read README.md for more information.