How to add right click context menu to /assets, which display it only for one file type

I want to add context menu when hitting right mouse button on the material file in project browser, but I don't want to display it when hitting right mouse button in other file type than Material.

So, I want to call something like this:

 [MenuItem("Assets/Open in Material Edit")]
         private static void OpenMaterialEdit(MenuCommand menuCommand)
         {
             for (int i = 0; i < Selection.objects.Length; i++)
             {
                 if (Selection.objects[i] is Material)
                 {
                     if (Get == null) Init();
                     Get.TargetMaterial = Selection.objects[i] as Material;
                     return;
                 }
             }
         }

But now it will be displayed on every file in project, when I want to have this option visible only for Material type.

There is something like: [MenuItem("CONTEXT/Material/Open in Material Edit")] But it's for hitting right mouse button on the added component inside inspector window, maybe there is something similar for assets file menu item?