Add write/read indices and commands handling to MidiMessage

Introduced `writeIndex` and `readIndex` for managing MIDI commands. Added `addMidiCommand`, `readMessage`, and `resetReadIndex` methods to enhance MIDI message manipulation. Ensured validation to limit commands to a maximum of 16.

src/commonMain/kotlin/nl/astraeus/midi/message/MidiMessage.kt

@@ -50,6 +50,8 @@ class TimedMidiMessage() : MidiMessage(
 ) {
   var timeToPlay by double("timeToPlay")
   var midi by blob("midi")
+  var writeIndex: Int = 0
+  var readIndex: Int = 0
 
   init {
     this.type = MidiMessageTypes.MIDI_DATA.typeId
@@ -70,6 +72,31 @@ class TimedMidiMessage() : MidiMessage(
     this.timeToPlay = timeToPlay
     val ba: ByteArray = data
     this.midi = SlicedByteArray(ba)
+    writeIndex = ba.size / 3
+  }
+
+  fun addMidiCommand(vararg data: Byte) {
+    check(writeIndex <= 45) {
+      "Can't add more than 16 commands to a midi message"
+    }
+    for (index in data.indices) {
+      midi[writeIndex++] = data[index]
+    }
+  }
+
+  fun readMessage(): ByteArray? {
+    check(writeIndex <= 45) {
+      "Can't read more than 16 commands from a midi message"
+    }
+    val result = ByteArray(3)
+    for (index in 0 ..< 3) {
+      result[index] = midi[readIndex++]
+    }
+    return result
+  }
+
+  fun resetReadIndex() {
+    readIndex = 0
   }
 
 }