feat(aktuelt): minimal viable news pages

[niccofyren]

Closes: #7

Exposes news pages on http://localhost:8000/api/v2/news with semi-realistic fields (in output and on admin pages). Still a lot of possible tweaks both to improve output structure and admin UI, but this should likely cover the minimum we need to replace existing WP articles.

Know questions

• How to best output body and intro content? Body allows various sections/blocks that can include more advanced or custom content types. For now we just use the defaults, but we might know/figure out better approach once frontend work starts.
• How to best organise admin UI? Wagtail allows for different ways of grouping fields, but we now dump everything into main content_panels in a semi-random order. Once we are more familiar with config and usage we should adjust as needed.