docs: add plugin setup guide

plugin/lib/commonlibf4/include/RE/C/ConcreteFormFactory.h

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+#pragma once
+
+#include "RE/I/IFormFactory.h"
+
+namespace RE
+{
+	template <class T, ENUM_FORM_ID ID = T::FORM_ID>
+	class __declspec(novtable) ConcreteFormFactory :
+		public IFormFactory  // 00
+	{
+	public:
+		[[nodiscard]] static ConcreteFormFactory* GetFormFactory()
+		{
+			const auto factories = GetFormFactories();
+			return static_cast<ConcreteFormFactory*>(factories[std::to_underlying(ID)]);
+		}
+
+		[[nodiscard]] T* Create() { return static_cast<T*>(DoCreate()); }
+
+		// members
+		const char* name{ nullptr };
+	};
+}