Add updateList documentation

[MAILPOET-4752]

doc/api_methods/UpdateList.md

@@ -0,0 +1,38 @@
+[back to list](../Readme.md)
+
+# Add Subscriber
+
+## `array updateList(array $list)`
+
+This method provides functionality for updating a list name or description.
+
+It returns the updated list. See [Get Lists](GetLists.md) for a list data structure description.
+
+## Arguments
+
+### `$list` (required)
+
+An associative array which contains list data.
+
+| Property               | Type         | Limits    | Description                |
+| ---------------------- | ------------ | --------- | -------------------------- |
+| id (required)          | string       | 11 chars  | A id of the list.          |
+| name (required)        | string       | 90 chars  | A name of the list.        |
+| description (optional) | string\|null | 250 chars | A description of the list. |
+
+## Error handling
+
+All expected errors from the API are exceptions of class `\MailPoet\API\MP\v1\APIException`.
+Code of the exception is populated to distinguish between different errors.
+
+An exception of base class `\Exception` can be thrown when something unexpected happens.
+
+Codes description:
+
+| Code | Description                                  |
+| ---- | -------------------------------------------- |
+| 5    | The list was not found by id                 |
+| 14   | Missing list name                            |
+| 15   | Trying to use a list that is already used    |
+| 18   | Missing list id                              |
+| 19   | The list couldn’t be updated in the database |