Adds jittering. (#4809)

Co-authored-by: Pieter-Jan Briers <pieterjan.briers+git@gmail.com>

Content.Server/Jittering/JitteringSystem.cs

@@ -0,0 +1,9 @@
+using Content.Shared.Jittering;
+
+namespace Content.Server.Jittering
+{
+    public class JitteringSystem : SharedJitteringSystem
+    {
+        // This entity system only exists on the server so it will be registered, otherwise we can't use SharedJitteringSystem...
+    }
+}