[Enhancement] Fixed toolbar title in page should be heading (h1)

[RasmusKjeldgaard]

• I have written a good issue

Describe the enhancement

With only a toolbarTitle, and no title, on a Kirby Page, the title becomes fixed in the toolbar.
The scenario in question can be seen here: https://cookbook.kirby.design/#/examples/page/fixed

Describe the solution you'd like

In the fixe state, the toolbar title should act as the page title and be marked up as a h1 for proper semantics.

Are there any additional context?

Current workaround is to use the *kirbyPageToolbarTitle directive on a h1 with a little bit of custom styling to make it look similar to the default fixed toolbarTitle.

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Checklist:

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Refinement

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