Run default addressables build conditionally (#231)

* Add asmdef and Addressable content build in the builder

* Move asmdef content into its own directory

* Mark UnityBuilderAction as Editor-only

dist/default-build-script/Assets/Editor/UnityBuilderAction/Versioning/GitException.cs

@@ -0,0 +1,14 @@
+using System;
+
+namespace UnityBuilderAction.Versioning
+{
+  public class GitException : InvalidOperationException
+  {
+    public readonly int code;
+
+    public GitException(int code, string errors) : base(errors)
+    {
+      this.code = code;
+    }
+  }
+}