Add leech to crusher (#17683)

Content.Shared/Weapons/Marker/LeechOnMarkerComponent.cs

@@ -0,0 +1,16 @@
+using Content.Shared.Damage;
+using Robust.Shared.GameStates;
+
+namespace Content.Shared.Weapons.Marker;
+
+/// <summary>
+/// Applies leech upon hitting a damage marker target.
+/// </summary>
+[RegisterComponent, NetworkedComponent]
+public sealed class LeechOnMarkerComponent : Component
+{
+    // TODO: Can't network damagespecifiers yet last I checked.
+    [ViewVariables(VVAccess.ReadWrite)]
+    [DataField("leech", required: true)]
+    public DamageSpecifier Leech = new();
+}

Content.Shared/Weapons/Marker/SharedDamageMarkerSystem.cs

@@ -12,6 +12,7 @@ public abstract class SharedDamageMarkerSystem : EntitySystem
     [Dependency] private readonly IGameTiming _timing = default!;
     [Dependency] private readonly INetManager _netManager = default!;
     [Dependency] private readonly SharedAudioSystem _audio = default!;
+    [Dependency] private readonly DamageableSystem _damageable = default!;
 
     public override void Initialize()
     {
@@ -29,6 +30,11 @@ public abstract class SharedDamageMarkerSystem : EntitySystem
         args.BonusDamage += component.Damage;
         RemCompDeferred<DamageMarkerComponent>(uid);
         _audio.PlayPredicted(component.Sound, uid, args.User);
+
+        if (TryComp<LeechOnMarkerComponent>(args.Used, out var leech))
+        {
+            _damageable.TryChangeDamage(args.User, leech.Leech, true, false, origin: args.Used);
+        }
     }
 
     public override void Update(float frameTime)