Revert "remove beatmaps.hpp (it's in the generated struct now)"

This reverts commit ae97d0dd46.

turns out this is still used xd

include/beatmaps.hpp

@@ -0,0 +1,12 @@
+#pragma once
+
+#include <filesystem>
+
+namespace fs = std::filesystem;
+
+struct DifficultySettings {
+    double hpDrainRate;
+    double circleSize;
+    double approachRate;
+    double overallDifficulty;
+};