Add sprite fades for occluding sprites (#13267)

Content.Shared/Sprite/SpriteFadeComponent.cs

@@ -0,0 +1,12 @@
+using Robust.Shared.GameStates;
+
+namespace Content.Shared.Sprite;
+
+/// <summary>
+/// If your client entity is behind this then the sprite's alpha will be lowered so your entity remains visible.
+/// </summary>
+[RegisterComponent, NetworkedComponent]
+public sealed class SpriteFadeComponent : Component
+{
+
+}