Create reusable heading components

[robines]

The first header is 2.25rem (36px) on desktop displays only, anything smaller and it's 1.875rem (30px). This is because 36px can look a bit too big on smaller displays.

Created issue #1240 for applying usage of the components across the project.

Screenshot

[magsyg]

Mulig å kanskje omgjøre til en felles header component? så slipper man å importere forskjellige H#

[robines]

@magsyg For tree-shakingen sin del så syns jeg ikke det

[Snorre98]

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