Per-map parallax support (#9786)

* Per-map parallax support

* Comments for future sloth

* c

* bet

* Fix exception

* VV support

* Fix parallax

* mem

* weightless sounds

* Gravity stuff

* placeholder coz im too lazy to stash don't @ me son

* decent clouds

* sky

* Fast parallax

* Imagine spelling

* Loicense

* perish

* Fix weightless status

Co-authored-by: metalgearsloth <metalgearsloth@gmail.com>

Content.Shared/Parallax/ParallaxComponent.cs

@@ -0,0 +1,28 @@
+using JetBrains.Annotations;
+using Robust.Shared.GameStates;
+
+namespace Content.Shared.Parallax;
+
+/// <summary>
+/// Handles per-map parallax
+/// </summary>
+[RegisterComponent, NetworkedComponent]
+public sealed class ParallaxComponent : Component
+{
+    // I wish I could use a typeserializer here but parallax is extremely client-dependent.
+    [DataField("parallax")]
+    public string Parallax = "Default";
+
+    [UsedImplicitly, ViewVariables(VVAccess.ReadWrite)]
+    // ReSharper disable once InconsistentNaming
+    public string ParallaxVV
+    {
+        get => Parallax;
+        set
+        {
+            if (value.Equals(Parallax)) return;
+            Parallax = value;
+            IoCManager.Resolve<IEntityManager>().Dirty(this);
+        }
+    }
+}