Fix gravity shenanigans (#12866)

Content.Shared/Gravity/GravityShakeComponent.cs

@@ -0,0 +1,17 @@
+using Robust.Shared.GameStates;
+using Robust.Shared.Serialization.TypeSerializers.Implementations.Custom;
+
+namespace Content.Shared.Gravity;
+
+/// <summary>
+/// Indicates this entity is shaking due to gravity changes.
+/// </summary>
+[RegisterComponent, NetworkedComponent]
+public sealed class GravityShakeComponent : Component
+{
+    [ViewVariables(VVAccess.ReadWrite), DataField("shakeTimes")]
+    public int ShakeTimes;
+
+    [DataField("nextShake", customTypeSerializer:typeof(TimeOffsetSerializer))]
+    public TimeSpan NextShake;
+}