docs: add plugin setup guide

plugin/lib/commonlibf4/include/RE/H/hkRotation.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include "RE/H/hkMatrix3.h"
+
+namespace RE
+{
+	class hkRotationf :
+		public hkMatrix3f
+	{
+	public:
+		constexpr hkRotationf() noexcept = default;
+
+		using hkMatrix3f::hkMatrix3f;
+	};
+	static_assert(sizeof(hkRotationf) == 0x30);
+}