Use microdata to emphasize the breadcrumb navigation for SEO

[kevmoo]

The breadcrumb navigation currently generated is not detected by Google Search.

https://developers.google.com/search/docs/advanced/structured-data/breadcrumb#microdata

Consider using the microdata annotation.

this is used by Flutter.dev and it does seem to be detected by search engines - see https://docs.flutter.dev/development/data-and-backend/state-mgmt/declarative