docs: add plugin setup guide

plugin/lib/commonlibf4/include/RE/F/FORM_ENUM_STRING.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include "RE/E/ENUM_FORM_ID.h"
+
+namespace RE
+{
+	class FORM_ENUM_STRING
+	{
+	public:
+		// members
+		ENUM_FORM_ID  formID;      // 00
+		const char*   formString;  // 08 - "GRUP"
+		std::uint32_t formCode;    // 10 - 'PURG'
+	};
+	static_assert(sizeof(FORM_ENUM_STRING) == 0x18);
+}