Simple End Disable

Disables the End. That's it. No config options, no commands. Does so by just not teleporting entities that go through it, and instead showing the player a message. Currently the message does not support translation, though if I have time to add it in, I will eventually do so. This works server-side, though if you have it on your client, it will disable the end in Single Player (Why would one want that, I do not know). To re-enable the End, just remove the mod. Code adapted from [github:ClemsonJames/progression](https://github.com/ClemsonJames/progression), specifically [this mixin](https://github.com/ClemsonJames/progression/blob/98d11444d224f23886867a4aafd30f3dd5ae9fda/src/main/java/com/jameslin/progression/mixin/EndPortalBlockMixin.java)