Add MidiMessageHandler for managing MIDI message handlers

Introduced `MidiMessageHandler` with support for adding and invoking handlers based on byte inputs. This enables more flexible and organized handling of MIDI messages within the application.

src/commonMain/kotlin/nl/astraeus/vst/MidiMessageHandler.kt

@@ -0,0 +1,16 @@
+package nl.astraeus.vst
+
+typealias MidiHandler = (Byte, Byte, Byte) -> Unit
+
+object MidiMessageHandler {
+  val handlers = mutableMapOf<Byte, MutableMap<Byte, MidiHandler>>()
+
+  fun addHandler(byte1: Byte, byte2: Byte = 0, handler: MidiHandler) {
+    handlers.getOrPut(byte1) { mutableMapOf() }[byte2] = handler
+  }
+
+  fun handle(byte1: Byte, byte2: Byte, byte3: Byte) {
+    handlers[byte1]?.get(byte2)?.invoke(byte1, byte2, byte3)
+  }
+
+}