Add mob retaliation (#19901)

Content.Server/NPC/Components/FactionExceptionTrackerComponent.cs

@@ -0,0 +1,16 @@
+using Content.Server.NPC.Systems;
+
+namespace Content.Server.NPC.Components;
+
+/// <summary>
+/// This is used for tracking entities stored in <see cref="FactionExceptionComponent"/>
+/// </summary>
+[RegisterComponent, Access(typeof(NpcFactionSystem))]
+public sealed partial class FactionExceptionTrackerComponent : Component
+{
+    /// <summary>
+    /// entities with <see cref="FactionExceptionComponent"/> that are tracking this entity.
+    /// </summary>
+    [DataField("entities")]
+    public HashSet<EntityUid> Entities = new();
+}