add ability to configure active slots for the enchant

src/main/java/me/youhavetrouble/enchantio/enchants/ReplantingEnchant.java

@@ -9,6 +9,7 @@ import net.kyori.adventure.text.Component;
 import org.bukkit.enchantments.Enchantment;
 import org.bukkit.inventory.EquipmentSlotGroup;
 import org.bukkit.inventory.ItemType;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.Collections;
 import java.util.HashSet;
@@ -44,12 +45,12 @@ public class ReplantingEnchant implements EnchantioEnchant {
     }
 
     @Override
-    public Key getKey() {
+    public @NotNull Key getKey() {
         return KEY;
     }
 
     @Override
-    public Component getDescription() {
+    public @NotNull Component getDescription() {
         return Component.translatable("enchantio.enchant.replanting", "Replanting");
     }
 
@@ -69,27 +70,27 @@ public class ReplantingEnchant implements EnchantioEnchant {
     }
 
     @Override
-    public EnchantmentRegistryEntry.EnchantmentCost getMinimumCost() {
+    public EnchantmentRegistryEntry.@NotNull EnchantmentCost getMinimumCost() {
         return minimumCost;
     }
 
     @Override
-    public EnchantmentRegistryEntry.EnchantmentCost getMaximumCost() {
+    public EnchantmentRegistryEntry.@NotNull EnchantmentCost getMaximumCost() {
         return maximumCost;
     }
 
     @Override
-    public Iterable<EquipmentSlotGroup> getActiveSlots() {
-        return Set.of(EquipmentSlotGroup.HAND);
+    public @NotNull Iterable<EquipmentSlotGroup> getActiveSlots() {
+        return Set.of(EquipmentSlotGroup.MAINHAND);
     }
 
     @Override
-    public Set<TagEntry<ItemType>> getSupportedItems() {
+    public @NotNull Set<TagEntry<ItemType>> getSupportedItems() {
         return supportedItemTags;
     }
 
     @Override
-    public Set<TagKey<Enchantment>> getEnchantTagKeys() {
+    public @NotNull Set<TagKey<Enchantment>> getEnchantTagKeys() {
         return Collections.unmodifiableSet(enchantTagKeys);
     }