Add Soul Dew item and make various minor changes

src/modifier/modifier-type.ts

@@ -681,6 +681,8 @@ export const modifierTypes = {
 
   SOOTHE_BELL: () => new PokemonFriendshipBoosterModifierType('Soothe Bell'),
 
+  SOUL_DEW: () => new PokemonHeldItemModifierType('Soul Dew', 'Increases the influence of a Pokémon\'s nature on its stats by 5% (additive)', (type, args) => new Modifiers.PokemonNatureWeightModifier(type, (args[0] as Pokemon).id)),
+
   AMULET_COIN: () => new ModifierType('Amulet Coin', 'Increases money rewards by 20%', (type, _args) => new Modifiers.MoneyMultiplierModifier(type)),
   GOLDEN_PUNCH: () => new PokemonHeldItemModifierType('Golden Punch', 'Grants 20% of damage inflicted as money', (type, args) => new Modifiers.DamageMoneyRewardModifier(type, (args[0] as Pokemon).id)),
   COIN_CASE: () => new ModifierType('Coin Case', 'After every 10th battle, receive 10% of your money in interest', (type, _args) => new Modifiers.MoneyInterestModifier(type)),
@@ -821,6 +823,7 @@ const modifierPool = {
       const friendshipBenefitPartyMemberCount = Math.min(party.filter(p => (pokemonEvolutions.hasOwnProperty(p.species.speciesId) && pokemonEvolutions[p.species.speciesId].find(e => e.condition && e.condition instanceof SpeciesFriendshipEvolutionCondition)) || p.moveset.find(m => m.moveId === Moves.RETURN)).length, 3);
       return friendshipBenefitPartyMemberCount * 3;
     }),
+    new WeightedModifierType(modifierTypes.SOUL_DEW, 3),
     new WeightedModifierType(modifierTypes.GOLDEN_PUNCH, 2),
     new WeightedModifierType(modifierTypes.GRIP_CLAW, 2),
     new WeightedModifierType(modifierTypes.HEALING_CHARM, 1),

src/modifier/modifier.ts

@@ -1232,6 +1232,34 @@ export class PokemonFriendshipBoosterModifier extends PokemonHeldItemModifier {
   }
 }
 
+export class PokemonNatureWeightModifier extends PokemonHeldItemModifier {
+  constructor(type: ModifierTypes.ModifierType, pokemonId: integer, stackCount?: integer) {
+    super(type, pokemonId, stackCount);
+  }
+
+  matchType(modifier: Modifier): boolean {
+    return modifier instanceof PokemonNatureWeightModifier;
+  }
+
+  clone(): PersistentModifier {
+    return new PokemonNatureWeightModifier(this.type, this.pokemonId, this.stackCount);
+  }
+  
+  apply(args: any[]): boolean {
+    const multiplier = args[1] as Utils.IntegerHolder;
+    if (multiplier.value !== 1) {
+      multiplier.value += 0.05 * this.getStackCount() * (multiplier.value > 1 ? 1 : -1);
+      return true;
+    }
+
+    return false;
+  }
+
+  getMaxHeldItemCount(pokemon: Pokemon): integer {
+    return 5;
+  }
+}
+
 export class MoneyMultiplierModifier extends PersistentModifier {
   constructor(type: ModifierType, stackCount?: integer) {
     super(type, stackCount);