Docfix: the default mode is the dynamic mode. (#4684)

* Docfix: the default mode is the dynamic mode.

Closes #4679

docs/guides/schemaless.md

@@ -57,15 +57,20 @@ indexing_settings:
 ```
 
 The `mode` attribute controls what should be done if an ingested document
-contains a field that is not defined in the document mapping. By default, it takes the `lenient` value. In `lenient` mode, the fields that do not appear in the document mapping will simply be ignored.
+contains a field that is not defined in the document mapping. By default, your index is in the `dynamic` mode. In `dynamic` mode, the fields that do not appear in the document mapping will be indexed in a schemaless fashion.
+See details in the [dynamic mode section](#dynamic-mode).
+
 
 If `mode` is set to `strict` on the other hand, documents containing fields
 that are not defined in the mapping will be entirely discarded.
 
-## Schemaless with a partial schema
+Finally the last possible value for `mode` is `lenient`. In lenient mode, fields that are not present in the field mapping will simply be ignored.
+
+## The dynamic mode: schemaless with a partial schema {#dynamic-mode}
 
-`mode` can take another value: `dynamic`.
+`mode` can take the value: `dynamic`.
 When set to dynamic, all extra fields will actually be mapped using a catch-all configuration.
+
 By default, this catch-all configuration indexes and stores all of these fields, but this can be configured by setting the [`dynamic_mapping` attribute](../configuration/index-config#mode).
 A minimalist, yet perfectly valid and useful index configuration is then: