WIP implementing TZX support

Core/Io/TzxBlocks.cs

@@ -0,0 +1,24 @@
+using System;
+
+namespace Core.Io
+{
+    // The base class all future TZX blocks will inherit from
+    public abstract class TzxBlock
+    {
+        public abstract int BlockId { get; }
+    }
+
+    // ID 0x10: Standard Speed Data Block
+    public class StandardSpeedBlock : TzxBlock
+    {
+        public override int BlockId => 0x10;
+
+        // How long to pause the tape in milliseconds after this block loads
+        public ushort PauseAfterMs { get; set; }
+
+        public ushort DataLength { get; set; }
+
+        // The actual tape bytes
+        public byte[] Data { get; set; } = Array.Empty<byte>();
+    }
+}