Chem guidebook (#17123)

* im good at atomizing. welcome to half-finished chem guides.

* wagh

* e

* save work

* aa

* woweee UI

* finishing the last of it

* don't actually update the engine :(

---------

Co-authored-by: moonheart08 <moonheart08@users.noreply.github.com>

Content.Shared/Chemistry/SharedChemistryGuideDataSystem.cs

@@ -0,0 +1,42 @@
+using Content.Shared.Chemistry.Reagent;
+using Robust.Shared.Prototypes;
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.Chemistry;
+
+/// <summary>
+/// This handles the chemistry guidebook and caching it.
+/// </summary>
+public abstract class SharedChemistryGuideDataSystem : EntitySystem
+{
+    [Dependency] protected readonly IPrototypeManager PrototypeManager = default!;
+
+    protected readonly Dictionary<string, ReagentGuideEntry> Registry = new();
+
+    public IReadOnlyDictionary<string, ReagentGuideEntry> ReagentGuideRegistry => Registry;
+}
+
+[Serializable, NetSerializable]
+public sealed class ReagentGuideRegistryChangedEvent : EntityEventArgs
+{
+    public ReagentGuideChangeset Changeset;
+
+    public ReagentGuideRegistryChangedEvent(ReagentGuideChangeset changeset)
+    {
+        Changeset = changeset;
+    }
+}
+
+[Serializable, NetSerializable]
+public sealed class ReagentGuideChangeset
+{
+    public Dictionary<string,ReagentGuideEntry> GuideEntries;
+
+    public HashSet<string> Removed;
+
+    public ReagentGuideChangeset(Dictionary<string, ReagentGuideEntry> guideEntries, HashSet<string> removed)
+    {
+        GuideEntries = guideEntries;
+        Removed = removed;
+    }
+}