feat: add the ability to use Sointu as a sync-tracker

There is a new "sync" opcode that saves the top-most signal every 256 samples to the new "syncBuffer" output. Additionally, you can enable saving the current fractional row as sync[0], avoiding calculating the beat in the shader, but also calculating the beat correctly when the beat is modulated.

tests/test_sync.yml

@@ -0,0 +1,20 @@
+bpm: 100
+rowsperbeat: 4
+score:
+    rowsperpattern: 16
+    length: 2
+    tracks:
+        - numvoices: 1
+          order: [0, 0]
+          patterns: [[64, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0]]
+patch:
+    - numvoices: 1
+      units:
+        - type: envelope
+          parameters: {attack: 64, decay: 64, gain: 128, release: 80, stereo: 0, sustain: 64}
+        - type: sync
+        - type: envelope
+          parameters: {attack: 95, decay: 64, gain: 128, release: 80, stereo: 0, sustain: 64}
+        - type: sync
+        - type: out
+          parameters: {gain: 128, stereo: 1}