feat: elytra unequip when locked but equipped

* Made the elytra get removed from the chestplate slot when it is
  locked, prevents user for dragging it into their chestplate when
  locked too
* Renamed config.Util to config.ConfigUtil
* Added placeholder locked & unlocked elytra textures to resources

src/main/java/xyz/devcomp/elytralock/ElytraLock.java

@@ -1,7 +1,8 @@
 package xyz.devcomp.elytralock;
 
 import xyz.devcomp.elytralock.config.ConfigHandler;
-import xyz.devcomp.elytralock.config.Util;
+import xyz.devcomp.elytralock.config.ConfigUtil;
+import xyz.devcomp.elytralock.events.ClientTickEndHandler;
 import xyz.devcomp.elytralock.events.HudRenderHandler;
 
 import org.lwjgl.glfw.GLFW;
@@ -10,6 +11,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import net.fabricmc.api.ClientModInitializer;
+import net.fabricmc.fabric.api.client.event.lifecycle.v1.ClientTickEvents;
 import net.fabricmc.fabric.api.client.keybinding.v1.KeyBindingHelper;
 import net.fabricmc.fabric.api.client.rendering.v1.HudRenderCallback;
 import net.fabricmc.loader.api.FabricLoader;
@@ -27,7 +29,7 @@ public class ElytraLock implements ClientModInitializer {
 
 	@Override
 	public void onInitializeClient() {
-		LOGGER.info("Elytra lock initializing!");
+		LOGGER.info("ElytraLock initializing!");
 
 		lockKeybind = KeyBindingHelper.registerKeyBinding(
 				new KeyBinding("key.elytralock.lock", InputUtil.Type.KEYSYM, GLFW.GLFW_KEY_J, "category.elytralock"));
@@ -35,7 +37,7 @@ public class ElytraLock implements ClientModInitializer {
 
 		client = MinecraftClient.getInstance();
 
-		if (Util.isYaclLoaded()) {
+		if (ConfigUtil.isYaclLoaded()) {
 			LOGGER.info("YACL_v3 is loaded, loading elytra toggle");
 			locked = new ConfigHandler().getInstance().toggle;
 		} else {
@@ -43,6 +45,9 @@ public class ElytraLock implements ClientModInitializer {
 		}
 
 		HudRenderCallback.EVENT.register(new HudRenderHandler());
+		ClientTickEvents.END_CLIENT_TICK.register(new ClientTickEndHandler());
+
+		LOGGER.info("Registered HUD_RENDER & END_CLIENT_TICK events successfully!");
 	}
 
 	public static boolean isLocked() {

src/main/java/xyz/devcomp/elytralock/config/ConfigUtil.java

@@ -2,7 +2,7 @@ package xyz.devcomp.elytralock.config;
 
 import xyz.devcomp.elytralock.ElytraLock;
 
-public class Util {
+public class ConfigUtil {
     public static boolean isYaclLoaded() {
         return ElytraLock.LOADER.isModLoaded("yet_another_config_lib_v3");
     }

src/main/java/xyz/devcomp/elytralock/events/ClientTickEndEvent.java

@@ -1,10 +0,0 @@
-package xyz.devcomp.elytralock.events;
-
-import net.minecraft.client.MinecraftClient;
-
-public class ClientTickEndEvent {
-    public void callbackHandler(MinecraftClient client) {
-        // Check if guy wearing elytra, if so, then remove
-        
-    }
-}

src/main/java/xyz/devcomp/elytralock/events/ClientTickEndHandler.java

@@ -0,0 +1,34 @@
+package xyz.devcomp.elytralock.events;
+
+import net.fabricmc.fabric.api.client.event.lifecycle.v1.ClientTickEvents.EndTick;
+import net.minecraft.client.MinecraftClient;
+import net.minecraft.entity.player.PlayerInventory;
+import net.minecraft.item.ItemStack;
+import net.minecraft.item.Items;
+import xyz.devcomp.elytralock.ElytraLock;
+
+public class ClientTickEndHandler implements EndTick {
+    public void onEndTick(MinecraftClient client) {
+        if (client.isWindowFocused() && ElytraLock.isLocked() && client.player != null) {
+            PlayerInventory inventory = client.player.getInventory();
+
+            // 0 -> boots 
+            // 1 -> leggings
+            // 2 -> chestplate
+            // 3 -> helmet
+            ItemStack chestArmor = inventory.armor.get(2);
+
+            if (chestArmor.isOf(Items.ELYTRA)) {
+                ElytraLock.LOGGER.info("Detected player wearing elytra even though it's locked");
+                ItemStack elytra = chestArmor.copyAndEmpty();
+                int inventorySlot = inventory.getSwappableHotbarSlot();
+                
+                boolean ok = inventory.insertStack(inventorySlot, elytra);
+
+                if (!ok) {
+                    ElytraLock.LOGGER.warn("Failed to remove equipped elytra, which is locked");
+                }
+            }
+        }
+    }
+}

src/main/java/xyz/devcomp/elytralock/integrations/ModMenuIntegration.java

@@ -1,7 +1,7 @@
 package xyz.devcomp.elytralock.integrations;
 
 import xyz.devcomp.elytralock.config.ConfigHandler;
-import xyz.devcomp.elytralock.config.Util;
+import xyz.devcomp.elytralock.config.ConfigUtil;
 
 import com.terraformersmc.modmenu.api.ConfigScreenFactory;
 import com.terraformersmc.modmenu.api.ModMenuApi;
@@ -10,7 +10,7 @@ public class ModMenuIntegration implements ModMenuApi {
     @Override
     public ConfigScreenFactory<?> getModConfigScreenFactory() {
         return (parent) -> {
-            if (!Util.isYaclLoaded())
+            if (!ConfigUtil.isYaclLoaded())
                 return parent;
             return new ConfigHandler().showGui(parent);
         };