Add product custom fields documentation

Author: octaedro

source/includes/wp-api-v3/_product-custom-fields.md

@@ -0,0 +1,61 @@
+# Product custom fields #
+
+The product custom fields API allows you to view the custom fields that have been recorded.
+
+## Product custom fields properties ##
+
+| Attribute | Type   | Description                                                                                                 |
+| --------- | ------ | ----------------------------------------------------------------------------------------------------------- |
+| `key`     | string | The custom field key.                                                                                       |
+| `value`   | string | The value set for the key.                                                                                  |
+
+## Retrieve product custom fields ##
+
+This API lets you retrieve filtered custom fields.
+
+<div class="api-endpoint">
+	<div class="endpoint-data">
+		<i class="label label-get">GET</i>
+		<h6>/wp-json//wc/v3/products/custom-fields/names</h6>
+	</div>
+</div>
+
+```shell
+curl https://example.com/wp-json/wc/v3/products/custom-fields/names \
+	-u consumer_key:consumer_secret
+```
+
+```javascript
+WooCommerce.get("products/custom-fields/names")
+  .then((response) => {
+    console.log(response.data);
+  })
+  .catch((error) => {
+    console.log(error.response.data);
+  });
+```
+
+```php
+<?php print_r($woocommerce->get('products/custom-fields/names')); ?>
+```
+
+```python
+print(wcapi.get("products/custom-fields/names").json())
+```
+
+```ruby
+woocommerce.get("products/custom-fields/names").parsed_response
+```
+
+> JSON response example:
+
+```json
+{
+	[
+		"Custom field 1",
+		"Custom field 2",
+		"Custom field 3",
+		"Custom field 4"
+	]
+}
+```

source/index.html.md

@@ -31,6 +31,7 @@ includes:
   - wp-api-v3/product-attributes
   - wp-api-v3/product-attribute-terms
   - wp-api-v3/product-categories
+  - wp-api-v3/product-custom-fields
   - wp-api-v3/product-shipping-classes
   - wp-api-v3/product-tags
   - wp-api-v3/product-reviews