Mob sensor screen is finally working

• I worked quite a bit on the mob sensor screen and finally got the dropdown working.
• The dropdown was honestly way more annoying than I expected. I had problems with the text not showing, the entries being weird when hovering, and moving the dropdown would only move the text instead of the whole thing.
• After messing with it for a while I got it working, with the mob names centered and the hover effect working too.
• Then I wanted the selected mob to actually save when I close the screen instead of resetting every time.
• Since the block is in main and the screen is in client, I had to figure out how to pass the BlockEntity to the screen without mixing the two.
• I added NBT saving to the Mob Sensor BlockEntity, so every sensor can save its own selected mob.
• I tested it with multiple sensors and it actually works, so one can be set to Zombie and another to Creeper and they both remember their settings.
• I also got HotSwap working, which made testing the GUI changes a lot easier.

Overall, I’m pretty happy with how the mob sensor is going. Now I just need to make it actually detect the mob instead of just remembering it, and add a texture to it, which will be dynamic.