Add docs about multiple sheet imports

Author: patrickbrouwers

.vuepress/3.1.js

@@ -40,6 +40,7 @@ module.exports = [
             'collection',
             'model',
             'importables',
+            'multiple-sheets',
             'heading-row',
             'batch-inserts',
             'chunk-reading',

3.1/imports/multiple-sheets.md

@@ -0,0 +1,27 @@
+# Multiple Sheets
+
+When a file has multiple sheets, each sheet will go through the import object. If you want to handle each sheet separately, you'll need to implement the `WithMultipleSheets` concern.
+
+The `sheets()` method expects an array of sheet import objects to be returned.
+
+```php
+namespace App\Imports;
+
+use Maatwebsite\Excel\Concerns\WithMultipleSheets;
+
+class UsersImport implements WithMultipleSheets {
+    
+    public function sheets(): array
+    {
+        return [
+            // Select by sheet index
+            0 => new FirstSheetImport(),
+            
+            // Select by sheet name
+            'Sheet2' => new SecondSheetImport
+        ];
+    }
+}
+```
+
+The `FirstSheetImport` can implement concerns like `ToCollection`, `ToModel`, ...