Add listeners for full setup (mostly useful for Fabric)

Signed-off-by: TheSilkMiner <thesilkminer@outlook.com>

Common/src/main/java/com/blamejared/crafttweaker/CraftTweakerCommon.java

@@ -75,6 +75,11 @@ public static void handlePlugins(final Stream<Class<? extends ICraftTweakerPlugi
         PLUGIN_MANAGER.get().loadPlugins();
     }
 
+    public static void handleFullSetupEnd() {
+
+        PLUGIN_MANAGER.get().broadcastEnd();
+    }
+
     public static void registerCommands(CommandDispatcher<CommandSourceStack> dispatcher, Commands.CommandSelection environment) {
 
         CTCommands.init(dispatcher, environment);

Common/src/main/java/com/blamejared/crafttweaker/api/plugin/ICraftTweakerPlugin.java

@@ -15,4 +15,6 @@ default void registerBracketParsers(final IBracketParserRegistrationHandler hand
 
     default void manageJavaNativeIntegration(final IJavaNativeIntegrationRegistrationHandler handler) {}
 
+    default void registerListeners(final IListenerRegistrationHandler handler) {}
+
 }

Common/src/main/java/com/blamejared/crafttweaker/api/plugin/IListenerRegistrationHandler.java

@@ -0,0 +1,7 @@
+package com.blamejared.crafttweaker.api.plugin;
+
+public interface IListenerRegistrationHandler {
+
+    void registerCraftTweakerLoadCompleteListener(final Runnable runnable);
+
+}

Common/src/main/java/com/blamejared/crafttweaker/impl/plugin/core/PluginManager.java

@@ -47,4 +47,9 @@ public void loadPlugins() {
         throw new UnsupportedOperationException("Not yet implemented");
     }
 
+    public void broadcastEnd() {
+
+        // TODO("")
+    }
+
 }