feat: Create new sub-page components

[arky]

Is your feature request related to a problem? Please describe.
Currently only two sub page components 'Drop case' 'Quotes' are available in the article design. You can only select them, but there is way to customize your own components nor save the changes you made as new sub-page components.

Use case:
The editor ways to show an article inset which has a heading and text. Since this article inset might be used in future, the editors want it the designer to create the page component and save it for future use.

It would be also great if such sub-page components are available for editors to use while writing their stories.

[DanSnow]

Do you mean you want to save the component as preset or do you want it completely customizable?