docs: add plugin setup guide

plugin/lib/commonlibf4/include/RE/N/NiTFlags.h

@@ -0,0 +1,18 @@
+#pragma once
+
+namespace RE
+{
+	template <class Integral, class>
+	class NiTFlags
+	{
+	public:
+		using integral_type = Integral;
+
+		static_assert(std::is_integral_v<integral_type>);
+
+		constexpr NiTFlags() noexcept {}  // NOLINT(moderinize-use-equals-default)
+
+		// members
+		integral_type flags{ 0 };  // 00
+	};
+}