[Enhancement] Header kirby-flag content.

[henrikvoetmand]

• [x] I have written a good issue

Describe the enhancement

Investment area in DRB wishes to use the Header "kirby-flag" slot to show custom content. E.g a flag icon and a short status text.

Describe the solution you'd like

Open the kirby-flag slot up to accept custom content.

Have you considered any alternatives?

No!

Are there any additional context?

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