Implement BattleEffects, add Thunderstorm

Assets/Battle/Effects/IncreaseMaxEnergyEffect.cs

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+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+public class IncreaseMaxEnergyEffect : IBattleEffect
+{
+    private int delta;
+
+    public IncreaseMaxEnergyEffect(int delta) {
+        this.delta = delta;
+    }
+
+    public void Apply(IBattleEffectResolver bc) {
+        bc.IncreaseMaxEnergy(this.delta);
+    }
+}

Assets/Battle/Effects/IncreaseMaxEnergyEffect.cs.meta

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