More abilities, refactor stealing held items

Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/Steadfast.cs

@@ -0,0 +1,26 @@
+namespace PkmnLib.Plugin.Gen7.Scripts.Abilities;
+
+/// <summary>
+/// Steadfast is an ability that raises the user's Speed each time it flinches.
+///
+/// <see href="https://bulbapedia.bulbagarden.net/wiki/Steadfast_(Ability)">Bulbapedia - Steadfast</see>
+/// </summary>
+[Script(ScriptCategory.Ability, "steadfast")]
+public class Steadfast : Script
+{
+    /// <inheritdoc />
+    public override void CustomTrigger(StringKey eventName, ICustomTriggerArgs args)
+    {
+        if (eventName != CustomTriggers.OnFlinch)
+            return;
+        if (args is not CustomTriggers.OnFlinchArgs flinchArgs)
+            return;
+
+        EventBatchId batchId = new();
+        flinchArgs.Move.Battle.EventHook.Invoke(new AbilityTriggerEvent(flinchArgs.Move.User)
+        {
+            BatchId = batchId,
+        });
+        flinchArgs.Move.User.ChangeStatBoost(Statistic.Speed, 1, true, false, batchId);
+    }
+}