Fix additional ambiguous reference warnings during sphinx build

docs/advanced_topics/documents/custom_document_model.md

@@ -1,3 +1,5 @@
+(custom_document_model)=
+
 # Custom document model
 
 An alternate `Document` model can be used to add custom behaviour and

docs/extending/extending_client_side.md

@@ -25,7 +25,7 @@ The simplest way is to add global JavaScript files via hooks, see [](insert_edit
 
 For JavaScript added when a specific Widget is used you can add an inner `Media` class to ensure that the file is loaded when the widget is used, see [Django's docs on their form `Media` class](https://docs.djangoproject.com/en/stable/topics/forms/media/#assets-as-a-static-definition).
 
-In a similar way, Wagtail's [template components](template_components) provide a `media` property or `Media` class to add scripts when rendered.
+In a similar way, Wagtail's [](./template_components) provide a `media` property or `Media` class to add scripts when rendered.
 
 These will ensure the added files are used in the admin after the core JavaScript admin files are already loaded.