feat(dsp): add core synthesizer oscillators, wavetable and voice engine

Source/NoiseOscillator.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#include <JuceHeader.h>
+#include "Params.h"
+
+namespace serum
+{
+
+// ===========================================================================
+// Per-voice white/pink noise generator.
+// ===========================================================================
+class NoiseOscillator
+{
+public:
+    void prepare (double sampleRate) { sr = sampleRate; reset(); }
+    void reset();
+
+    void noteOn (juce::uint32 seed);
+
+    // Accumulate into out.
+    void processAdd (int type, float level, float& out) noexcept;
+
+private:
+    double        sr = 44100.0;
+    juce::Random  rng;
+    float         pinkB0 = 0.0f, pinkB1 = 0.0f, pinkB2 = 0.0f;
+};
+
+} // namespace serum