docs: Incude advanced-migration in sidebar
<ul>
{{ doc("docs/extras/deployment", "Deployment") }}
{{ doc("docs/extras/advanced-integration", "Advanced Integration") }}
+ {{ doc("docs/extras/advanced-migration", "Advanced Migration") }}
{{ doc("docs/extras/testing", "Testing") }}
{{ doc("docs/extras/api", "API") }}
{{ doc("docs/extras/contribs", "Community tools") }}
