Adds a new template part for the Navigation block called WP_TEMPLATE_PART_AREA_NAVIGATION_OVERLAY, corresponding area definition in block-template-utils.php to support navigation overlay template parts.
Also adds the navigation block pattern category registration in block-patterns.php and five new navigation overlay block patterns.
Reviewed by mikachan, get_dave.
Props onemaggie, scruffian, get_dave, mikachan, wildworks.
Fixes#64589.
Built from https://develop.svn.wordpress.org/trunk@61609
git-svn-id: http://core.svn.wordpress.org/trunk@60920 1a063a9b-81f0-0310-95a4-ce76da25c4cd
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