Add MidiMessageHandler for MIDI event handling

Introduced `MidiMessageHandler` to process and handle MIDI messages with customizable handlers for specific byte patterns. This addition improves extensibility and keeps MIDI message processing modular and organized.

audio-worklet/src/commonMain/kotlin/nl/astraeus/vst/midi/MidiMessageHandler.kt

@@ -0,0 +1,82 @@
+package nl.astraeus.vst.midi
+
+typealias MidiHandler = (Byte, Byte, Byte) -> Unit
+
+val Byte.channel: Byte
+  get() {
+    return (this.toInt() and 0x0F).toByte()
+  }
+
+val Byte.command: Byte
+  get() {
+    return ((this.toInt() and 0xF0) shr 4).toByte()
+  }
+
+val Byte.channelCommand: Boolean
+  get() {
+    return this.command >= 8 && this.command <= 13
+  }
+
+class MidiMessageHandler(
+  var channel: Byte = -1
+) {
+  val singleByteHandlers = mutableMapOf<Byte, MidiHandler>()
+  val doubleByteHandlers = mutableMapOf<Byte, MutableMap<Byte, MidiHandler>>()
+
+  fun addHandler(
+    byte1: Byte,
+    byte2: Byte = 0,
+    handler: MidiHandler
+  ) {
+    val b1 = if (byte1.channelCommand) {
+      (byte1.toInt() and 0xF0).toByte()
+    } else {
+      byte1
+    }
+    if (byte2 == 0.toByte()) {
+      singleByteHandlers[b1] = handler
+    } else {
+      val map = doubleByteHandlers.getOrPut(b1) {
+        mutableMapOf()
+      }
+      map[byte2] = handler
+    }
+  }
+
+  fun addHandler(
+    byte1: Int,
+    byte2: Int = 0,
+    handler: MidiHandler
+  ) = addHandler(
+    byte1.toByte(),
+    byte2.toByte(),
+    handler
+  )
+
+  fun handle(
+    byte1: Byte,
+    byte2: Byte,
+    byte3: Byte
+  ) {
+    if (
+      channel < 0 ||
+      !byte1.channelCommand ||
+      (byte1.channelCommand && channel == byte1.channel)
+    ) {
+      val b1 = if (byte1.channelCommand) {
+        (byte1.toInt() and 0xF0).toByte()
+      } else {
+        byte1
+      }
+
+      if (doubleByteHandlers.containsKey(b1)) {
+        doubleByteHandlers[b1]?.get(byte2)?.invoke(byte1, byte2, byte3)
+      } else if (singleByteHandlers.containsKey(b1)) {
+        singleByteHandlers[b1]?.invoke(byte1, byte2, byte3)
+      } else {
+        println("Unhandled message: $byte1 $byte2 $byte3")
+      }
+    }
+  }
+
+}