5 new triggers: EmptyContainers, Knockdown, Stun, TriggerOnThrowDoHit (#41472)

* ideas

* finish components

* systems

* one more

* requested

---------

Co-authored-by: iaada <iaada@users.noreply.github.com>

Content.Shared/Trigger/Components/Effects/KnockdownOnTriggerComponent.cs

@@ -0,0 +1,36 @@
+using Robust.Shared.GameStates;
+
+namespace Content.Shared.Trigger.Components.Effects;
+
+/// <summary>
+/// Trigger effect for sending the target sidewise (crawling).
+/// Knockdowns the user if <see cref="BaseXOnTriggerComponent.TargetUser"/> is true.
+/// </summary>
+[RegisterComponent, NetworkedComponent, AutoGenerateComponentState]
+public sealed partial class KnockdownOnTriggerComponent : BaseXOnTriggerComponent
+{
+    /// <summary>
+    /// How long the target is forced to be on the ground.
+    /// </summary>
+    [DataField, AutoNetworkedField]
+    public TimeSpan KnockdownAmount =  TimeSpan.FromSeconds(1);
+
+    /// <summary>
+    /// If true, refresh the duration.
+    /// If false, time is added on-top of any existing forced knockdown.
+    /// </summary>
+    [DataField, AutoNetworkedField]
+    public bool Refresh = true;
+
+    /// <summary>
+    /// Should the entity try and stand automatically?
+    /// </summary>
+    [DataField, AutoNetworkedField]
+    public bool AutoStand = true;
+
+    /// <summary>
+    /// Should the entity drop their items upon first being knocked down?
+    /// </summary>
+    [DataField, AutoNetworkedField]
+    public bool Drop = true;
+}