feat: add CommandRegistration struct

CommandHook/CommandRegistration.cs

@@ -0,0 +1,19 @@
+namespace CommandHook;
+
+public struct CommandRegistration
+{
+    public readonly string CommandFilter;
+    public readonly CommandHookDelegate? Before;
+    public readonly CommandHookDelegate? After;
+
+    public CommandRegistration(
+        string commandFilter,
+        CommandHookDelegate? before,
+        CommandHookDelegate? after
+    )
+    {
+        CommandFilter = commandFilter;
+        Before = before;
+        After = after;
+    }
+}