refactor: move custom config under extra

Removes a startup warning about an unknown configuration directive.

Refs: https://www.mkdocs.org/user-guide/configuration/#extra

Signed-off-by: Mike Fiedler <[email protected]>

Author: miketheman

mkdocs.yml

@@ -1,5 +1,4 @@
 site_name: Python Software Foundation Policies
-preview: !ENV [PREVIEW, "False"]
 theme:
   name: material
   custom_dir: ./overrides
@@ -23,6 +22,7 @@ plugins:
       fallback_to_build_date: true
 extra:
   homepage: https://python.org/psf/
+  preview: !ENV [PREVIEW, "False"]
 site_url: https://policies.python.org/
 repo_url: https://github.com/psf/policies
 

overrides/main.html

@@ -1,6 +1,6 @@
 {% extends "base.html" %}
 
-{% block announce %}{% if config.preview %}
+{% block announce %}{% if config.extra.preview %}
   <p>This is a <strong>preview</strong> of provisional changes to our policies.</p>
   <p>Any differences between the contents of these pages and the policies published at https://policies.python.org/ are <strong>not</strong> legally binding.</p>
 {% endif %}{% endblock %}