Feature/improve stepper

Refactor the Stepper component to adapt to the design
Added new functionality so it is possible to hide the next and back buttons so the developer can make custom buttons
I added a mobile version that gets viewed if it is on mobile devices. It is possible to send a prop to use the mobile version instead of the desktop version.
Added new functionality so it is possible to have a vertical stepper.
Change icons and colors to meet the design.

NOTE

Some CSS tokens are wrong, I have highlighted them with TODOs
The Documentation is not finished, this is because I need to implement the demo as a complex component since I need to add Steps array,s, and functions. But to implement the documentation in the Introduction Section I need to update the design-system version in the SandboxPreview.vue file so it gets the latest Stepper component.
To make it possible to test I have used the NVE-stepper-demo component, this should be removed after the documentation is finished.

NVE / Designsystem