feat(tracker): add menu to load instrument presets

The presets are embedded in the executable, so there's no additional files.

Closes #91

tracker/presets/snare.yml

@@ -0,0 +1,36 @@
+name: Snare
+numvoices: 1
+units:
+    - type: envelope
+      id: 1
+      parameters: {attack: 0, decay: 75, gain: 32, release: 0, stereo: 0, sustain: 0}
+    - type: send
+      id: 2
+      parameters: {amount: 128, port: 4, sendpop: 0, target: 1}
+    - type: envelope
+      id: 3
+      parameters: {attack: 0, decay: 70, gain: 128, release: 0, stereo: 0, sustain: 0}
+    - type: distort
+      id: 4
+      parameters: {drive: 8, stereo: 0}
+    - type: send
+      id: 6
+      parameters: {amount: 76, port: 0, sendpop: 1, target: 26}
+    - type: noise
+      id: 25
+      parameters: {gain: 128, shape: 64, stereo: 0}
+    - type: oscillator
+      id: 26
+      parameters: {color: 128, detune: 64, gain: 128, lfo: 0, phase: 64, shape: 64, stereo: 0, transpose: 64, type: 0}
+    - type: addp
+      id: 10
+      parameters: {stereo: 0}
+    - type: mulp
+      id: 11
+      parameters: {stereo: 0}
+    - type: pan
+      id: 12
+      parameters: {panning: 64, stereo: 0}
+    - type: outaux
+      id: 13
+      parameters: {auxgain: 0, outgain: 32, stereo: 1}