add helper to custom field and document

docs/Schema.md

@@ -230,7 +230,7 @@ class UpdatePassword extends RelayMutation
 Create a custom field:
 
 ```bash
-php artisan relay:make:field AvatarField
+php artisan relay:make:field Avatar
 ```
 
 ```php
@@ -243,7 +243,7 @@ use GraphQL\Type\Definition\Type;
 use Nuwave\Relay\Support\Definition\GraphQLField;
 use Nuwave\Relay\Traits\GlobalIdTrait;
 
-class AvatarField extends GraphQLField
+class Avatar extends GraphQLField
 {
     /**
      * Field attributes.
@@ -300,6 +300,26 @@ class AvatarField extends GraphQLField
 }
 ```
 
+**To use the field in your Type(s):**
+
+```php
+<?php
+// TypeClass ...
+
+/**
+ * Available fields of Type.
+ *
+ * @return array
+ */
+public function relayFields()
+{
+    return [
+        'avatar' => Avatar::field()
+    ]
+}
+
+```
+
 ### Schema File
 
 The ```schema.php``` file you create is similar to Laravel's ```routes.php``` file. It used to declare your Types, Mutations and Queries to be used by GraphQL. Similar to routes, you can group your schema by namespace as well as add middleware to your Queries and Mutations.

src/Support/Definition/GraphQLField.php

@@ -152,6 +152,16 @@ public function toArray()
         return $this->getAttributes();
     }
 
+    /**
+     * Transform into field array.
+     *
+     * @return array
+     */
+    public static function field()
+    {
+        return (new static)->toArray();
+    }
+
     /**
      * Dynamically retrieve the value of an attribute.
      *