Documentation: Put examples for config to the start of the section (p…

…ydantic#2615)

* Put examples to the start of the section

I think this is where they belong, they were in the middle of the list of config options somewhere near the end.

* Add "options" in table of contents

* tweak

Co-authored-by: Eric Jolibois <em.jolibois@gmail.com>

docs/usage/model_config.md

@@ -1,6 +1,23 @@
 Behaviour of _pydantic_ can be controlled via the `Config` class on a model or a _pydantic_ dataclass.
 
-Options:
+```py
+{!.tmp_examples/model_config_main.py!}
+```
+_(This script is complete, it should run "as is")_
+
+Also, you can specify config options as model class kwargs:
+```py
+{!.tmp_examples/model_config_class_kwargs.py!}
+```
+_(This script is complete, it should run "as is")_
+
+Similarly, if using the `@dataclass` decorator:
+```py
+{!.tmp_examples/model_config_dataclass.py!}
+```
+_(This script is complete, it should run "as is")_
+
+## Options
 
 **`title`**
 : the title for the generated JSON Schema
@@ -74,7 +91,7 @@ Options:
   for use with `orm_mode`
 
 **`alias_generator`**
-: a callable that takes a field name and returns an alias for it
+: a callable that takes a field name and returns an alias for it (see [the dedicated section](#alias-generator))
 
 **`keep_untouched`**
 : a tuple of types (e.g. descriptors) for a model's default values that should not be changed during model creation and will
@@ -92,24 +109,6 @@ not be included in the model schemas. **Note**: this means that attributes on th
 **`json_encoders`**
 : a `dict` used to customise the way types are encoded to JSON; see [JSON Serialisation](exporting_models.md#modeljson)
 
-```py
-{!.tmp_examples/model_config_main.py!}
-```
-_(This script is complete, it should run "as is")_
-
-Also, you can specify config options as model class kwargs:
-```py
-{!.tmp_examples/model_config_class_kwargs.py!}
-```
-_(This script is complete, it should run "as is")_
-
-Similarly, if using the `@dataclass` decorator:
-```py
-{!.tmp_examples/model_config_dataclass.py!}
-```
-_(This script is complete, it should run "as is")_
-
-
 **`underscore_attrs_are_private`**
 : whether to treat any underscore non-class var attrs as private, or leave them as is; See [Private model attributes](models.md#private-model-attributes)