Implement BattleEffects, add Thunderstorm

Assets/Battle/Cards/CardThunderstorm.cs

@@ -0,0 +1,17 @@
+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+public class CardThunderstorm : BaseCard
+{
+    public CardThunderstorm(BattleParticipant owner)
+        : base(owner, CardId.Thunderstorm, "Thunderstorm", 3, CardType.Enchantment,
+            "Adds 1 energy.") {
+    }
+
+    public override IEnumerator Use(IBattleEffectApplier effectApplier, BattlePlayerControls playerControls) {
+        Debug.Log("A storm is brewing.");
+        effectApplier.Apply(new IncreaseMaxEnergyEffect(1));
+        yield break;
+    }
+}