rename keyword: extract_binds => extractors

docs/extraction-and-validation.md

@@ -24,7 +24,7 @@ Suppose we get the following HTTP response.
 }
 ```
 
-In `extract_binds` and `validators`, we can do chain operation to extract data field in HTTP response.
+In `extractors` and `validators`, we can do chain operation to extract data field in HTTP response.
 
 For instance, if we want to get `Content-Type` in response headers, then we can specify `headers.content-type`; if we want to get `first_name` in response content, we can specify `content.person.name.first_name`.
 
@@ -46,7 +46,7 @@ content.person.cities.1
 ```
 
 ```yaml
-extract_binds:
+extractors:
     - content_type: headers.content-type
     - first_name: content.person.name.first_name
 validators: