Changed AssetsHelpers from editor window to context menu workflow.

Editor/SettingProvider/ArtToolsSettings.cs

@@ -0,0 +1,23 @@
+using UnityEditor;
+
+namespace Misaki.ArtToolEditor
+{
+    [FilePath("ProjectSettings/ArtToolsSettings.asset", FilePathAttribute.Location.ProjectFolder)]
+    internal class ArtToolsSettings : ScriptableSingleton<ArtToolsSettings>
+    {
+        internal SerializedObject GetSerializedObject()
+        {
+            return new SerializedObject(this);
+        }
+
+        internal void Save()
+        {
+            Save(true);
+        }
+
+        private void OnDisable()
+        {
+            Save();
+        }
+    }
+}

Editor/SettingProvider/ArtToolsSettings.cs.meta

@@ -0,0 +1,2 @@
+fileFormatVersion: 2
+guid: bf481249c6daba5458a7ee8fda5c632b