added MorphOne relation class

Author: CihanSenturk

src/Traits/Sortable.php

@@ -8,6 +8,7 @@
 use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\HasOne;
+use Illuminate\Database\Eloquent\Relations\MorphOne;
 use Illuminate\Support\Arr;
 use Illuminate\Support\Str;
 use Illuminate\Support\Facades\Schema;