docs: add plugin setup guide

plugin/lib/commonlibf4/include/RE/S/SpecialRefData.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#include "RE/U/UnloadedRefData.h"
+
+namespace RE
+{
+	class SpecialRefData
+	{
+	public:
+		// members
+		BGSLocationRefType* type;     // 00
+		UnloadedRefData     refData;  // 08
+	};
+	static_assert(sizeof(SpecialRefData) == 0x18);
+}