Adds disarm action (#2950)

* Adds disarming

* Disarm acts

* yaml

* much better icon for disarm

* Apply Remie's suggestions, improve code!

Content.Server/Interfaces/GameObjects/IDisarmedAct.cs

@@ -0,0 +1,42 @@
+using System;
+using Robust.Shared.Interfaces.GameObjects;
+
+namespace Content.Server.Interfaces.GameObjects
+{
+    /// <summary>
+    ///     Implements behavior when an entity is disarmed.
+    /// </summary>
+    public interface IDisarmedAct
+    {
+        /// <summary>
+        ///     Behavior when the entity is disarmed.
+        ///     Return true to prevent the default disarm behavior,
+        ///     or rest of IDisarmAct behaviors that come after this one from happening.
+        /// </summary>
+        bool Disarmed(DisarmedActEventArgs eventArgs);
+
+        /// <summary>
+        ///     Priority for this disarm act.
+        ///     Used to determine act execution order.
+        /// </summary>
+        int Priority => 0;
+    }
+
+    public class DisarmedActEventArgs : EventArgs
+    {
+        /// <summary>
+        ///     The entity being disarmed.
+        /// </summary>
+        public IEntity Target { get; init; }
+
+        /// <summary>
+        ///     The entity performing the disarm.
+        /// </summary>
+        public IEntity Source { get; init; }
+
+        /// <summary>
+        ///     Probability for push/knockdown.
+        /// </summary>
+        public float PushProbability { get; init; }
+    }
+}