Update doc

Author: GromNaN

README.md

@@ -631,6 +631,17 @@ $bars = Bar::raw(function ($collection) {
 });
 ```
 
+**Other operators**
+
+You can use any [MongoDB query operator](https://www.mongodb.com/docs/manual/reference/operator/query/#query-selectors) with the `where` function:
+
+```php
+$bars = Bar::where('qty', 'all', [
+    [ '$elemMatch' => [ 'size' => 'M', 'num' => [ '$gt' => 50] ] ],
+    [ '$elemMatch' => [ 'num' => 100, 'color' => 'green' ] ],
+])->get();
+```
+
 ### Inserts, updates and deletes
 
 Inserting, updating and deleting records works just like the original Eloquent. Please check [Laravel Docs' Eloquent section](https://laravel.com/docs/6.x/eloquent).