Use constant for column argument

Author: jhae-de

README.md

@@ -59,7 +59,7 @@ The filter takes up to three arguments to customize it to your needs.
         <td>Column</td>
         <td>String</td>
         <td>The name of the database column on which the selected date range should be applied to.</td>
-        <td>"created_at"</td>
+        <td>Illuminate\Database\Eloquent\Model::CREATED_AT</td>
     </tr>
     <tr>
         <td>Settings</td>

src/DateRangeFilter.php

@@ -4,6 +4,7 @@
 
 use Carbon\Carbon;
 use Illuminate\Database\Eloquent\Builder;
+use Illuminate\Database\Eloquent\Model;
 use Illuminate\Http\Request;
 use InvalidArgumentException;
 use Laravel\Nova\Filters\Filter;
@@ -26,7 +27,7 @@ class DateRangeFilter extends Filter
      */
     protected $column;
 
-    public function __construct(string $name = 'Created at', string $column = 'created_at', array $config = [])
+    public function __construct(string $name = 'Created at', string $column = Model::CREATED_AT, array $config = [])
     {
         $this->name = $name;
         $this->column = $column;