fix: refactor code structure into files (#8)

closes #7

Co-authored-by: HiveBeats <e1lama@protonmail.com>
Reviewed-on: #8

settings.h

@@ -0,0 +1,18 @@
+#ifndef SETTINGS_H
+#define SETTINGS_H
+
+#define SAMPLE_RATE 48000.f
+#define BPM 120.f
+#define BEAT_DURATION 60.f/BPM
+#define PITCH_STANDARD 440.f
+#define VOLUME 0.5f
+#define ATTACK_MS 100.f
+#define STREAM_BUFFER_SIZE 4096
+
+#define SYNTH_PI 3.1415926535f
+#define SYNTH_VOLUME 0.5f
+
+#define WINDOW_WIDTH 640
+#define WINDOW_HEIGHT 480
+
+#endif