add doc about list user configuration parameter

docs/contents/workers/yaml.md

@@ -120,6 +120,7 @@ A parameter is defined using the following settings:
     - `float`
     - `string`
     - `enum`
+    - `list`
     - `dict`
 
 `default`
@@ -131,6 +132,9 @@ A parameter is defined using the following settings:
 `choices`
 : Optional. A list of options for `enum` type parameters.
 
+`subtype`
+: Optional. The type of the elements of `list` type parameters.
+
 This definition allows for both validation of the input and the display of a form to make configuring workers easy for Arkindex users.
 
 ![User configuration](user_configuration/configuration_form.png "User configuration form on Arkindex")
@@ -228,6 +232,29 @@ Which will result in the following display for the user:
 
 ![Enum-type parameter](user_configuration/enum_config.png "Example enum-type parameter.")
 
+#### List parameters
+
+List-type parameters must be defined using a `title`, the `list` `type` and a `subtype` for the elements inside the list. You can also set a `default` value for this parameter, which must be a list containing elements of the given `subtype`, as well as make it a `required` parameter, which prevents users from leaving it blank.
+
+The allowed `subtype`s are `int`, `float` and `string`.
+
+In the configuration form, list parameters are displayed as rows of input fields.
+
+For example, a list-type parameter can be defined like this:
+
+```yaml
+a_list:
+  title: A List of Values
+  type: list
+  subtype: int
+  default: [4, 3, 12]
+```
+
+Which will result in the following display for the user:
+
+![List-type parameter](user_configuration/list_config.png "Example list-type parameter.")
+
+
 #### Dictionary parameters
 
 Dictionary-type parameters must be defined using a `title`, the `dict` `type`. You can also set a `default` value for this parameter, which must be one a dictionary, as well as make it a `required` parameter, which prevents users from leaving it blank. You can use dictionary parameters for example to specify a correspondence between the classes that are predicted by a worker and the elements that are created on Arkindex from these predictions.