Enable commands in all environments

- Many command-related fixes and improvements
- Added test environment for easier development

fabric/src/main/java/eu/midnightdust/fabric/core/MidnightLibFabric.java

@@ -2,13 +2,13 @@ package eu.midnightdust.fabric.core;
 
 import eu.midnightdust.core.MidnightLib;
 import net.fabricmc.api.ClientModInitializer;
-import net.fabricmc.api.DedicatedServerModInitializer;
 import net.fabricmc.api.EnvType;
 import net.fabricmc.api.Environment;
+import net.fabricmc.api.ModInitializer;
 
-public class MidnightLibFabric implements ClientModInitializer, DedicatedServerModInitializer {
+public class MidnightLibFabric implements ModInitializer, ClientModInitializer {
     @Override @Environment(EnvType.CLIENT)
     public void onInitializeClient() {MidnightLib.onInitializeClient();}
-    @Override @Environment(EnvType.SERVER)
-    public void onInitializeServer() {MidnightLib.onInitializeServer();}
+    @Override
+    public void onInitialize() {MidnightLib.onInitialize();}
 }

fabric/src/main/resources/fabric.mod.json

@@ -29,10 +29,10 @@
 
     "environment": "*",
     "entrypoints": {
-        "client": [
+        "main": [
             "eu.midnightdust.fabric.core.MidnightLibFabric"
         ],
-        "server": [
+        "client": [
             "eu.midnightdust.fabric.core.MidnightLibFabric"
         ],
         "modmenu": [