add doc

docs/en/latest/plugins/workflow.md

@@ -36,7 +36,7 @@ The `workflow` plugin is used to introduce [lua-resty-expr](https://github.com/a
 
 | Name                         | Type          | Required | Default | Valid values | Description                                                  |
 | ---------------------------- | ------------- | -------- | ------- | ------------ | ------------------------------------------------------------ |
-| rules.case                   | array[array]  | True     |         |              | List of variables to match for filtering requests for conditional traffic split. It is in the format `{variable operator value}`. For example, `{"arg_name", "==", "json"}`. The variables here are consistent with NGINX internal variables. For details on supported operators, you can refer to [lua-resty-expr](https://github.com/api7/lua-resty-expr#operator-list). |
+| rules.case                   | array[array]  | False     |         |              | List of variables to match for filtering requests for conditional traffic split. It is in the format `{variable operator value}`. For example, `{"arg_name", "==", "json"}`. The variables here are consistent with NGINX internal variables. For details on supported operators, you can refer to [lua-resty-expr](https://github.com/api7/lua-resty-expr#operator-list). |
 | rules.actions                | array[object] | True     |         |              | The action to be performed when the case matches successfully. Currently, only one element is supported in actions. The first child element of the actions' only element can be `return` or `limit-count`. |
 
 ### `actions` Attributes
@@ -58,6 +58,7 @@ The `workflow` plugin is used to introduce [lua-resty-expr](https://github.com/a
 :::note
 
 In `rules`, match `case` in order according to the index of the `rules`, and execute `actions` directly if `case` match.
+If `case` is missing, the default behavior is to match.
 
 :::