Enhanced Mob Spawners

Fixes zero block drops when having disable_silk_touch set to 1. #109

• fixed server crash #106

• Update to 1.21.1
• WIP: Slash commands for changing config values ingame. See this PR for details.
• Changed so that when spawner has no spawns left (with limited spawns), the egg is still present inside.

• Backported mod version 1.2.6 to 1.20.1 which fixes two issues: #87 and #83

Update to 1.20.4-1.2.5

• fixed: disable silk touch in config will prevent a silk touch enchant to drop the spawner.
• the mod will now accept the naming format: modid:spawn_egg_entity, which is used by some mods.