Add Movable Amethyst Rule (#894)

* Add Pushable Amethyst Rule

As discussed in #79 of ilmangos peaceful challenge. He said he'd do it, I figured I could beat him to the punch :)
https://youtu.be/0-fAKpr_J8k?t=1076

* Name change - movableAmethyst

Co-authored-by: hugeblank <hugeblank@gmail.com>

src/main/resources/carpet.mixins.json

@@ -89,6 +89,7 @@
     "ServerWorld_onePlayerSleepingMixin",
     "CoralBlockMixin",
     "CoralFeatureMixin",
+    "BuddingAmethystBlock_getPistonBehaviorMixin",
     "FluidBlock_renewableBlackstoneMixin",
     "FluidBlock_renewableDeepslateMixin",
     "LavaFluid_renewableDeepslateMixin",