docs: add plugin setup guide

plugin/lib/commonlibf4/include/RE/T/TESMagicCasterForm.h

@@ -0,0 +1,11 @@
+#pragma once
+
+namespace RE
+{
+	class TESMagicCasterForm
+	{
+	public:
+		static constexpr auto RTTI{ RTTI::TESMagicCasterForm };
+	};
+	static_assert(std::is_empty_v<TESMagicCasterForm>);
+}