chore: initialize standalone UPM package

ShrinkCommandEventBusBridgeOptions.cs

@@ -0,0 +1,10 @@
+#nullable enable
+
+namespace ShrinkCommand.Integration
+{
+    public sealed class ShrinkCommandEventBusBridgeOptions
+    {
+        public string ServiceName { get; set; } = ShrinkCommandConstants.DefaultServiceName;
+        public IShrinkCommandSource? DefaultSource { get; set; }
+    }
+}