Re-organize all projects (#4166)

Content.Shared/Slippery/SlipperySystem.cs

@@ -0,0 +1,20 @@
+#nullable enable
+using System.Linq;
+using JetBrains.Annotations;
+using Robust.Shared.GameObjects;
+
+namespace Content.Shared.Slippery
+{
+    [UsedImplicitly]
+    public class SlipperySystem : EntitySystem
+    {
+        /// <inheritdoc />
+        public override void Update(float frameTime)
+        {
+            foreach (var slipperyComp in ComponentManager.EntityQuery<SlipperyComponent>().ToArray())
+            {
+                slipperyComp.Update();
+            }
+        }
+    }
+}