[Enhancement] Fix list with shape none, to have its items and borders transparent

[x] I have written a good issue

Describe the enhancement

In the cookbook it is written that a list with no shape: "Removes background, border, shadow and padding from the list and the list item containers...". However the borders and background of the list items are still shown.

Describe the solution you'd like

Make background transparent and remove border for list items when list has shape "none".

Have you considered any alternatives?

Are there any additional context?

Checklist:

The following tasks should be carried out in sequence in order to follow the process of contributing correctly.

Refinement

[ ] Request that the issue is UX refined
[ ] Request that the issue is tech refined; do not proceed until this is done.

Implementation

The contributor who wants to implement this issue should:

[ ] Make sure you have read: "Before you get coding".
[ ] Signal to others you are working on the issue by assigning yourself.
[ ] Create a branch from the develop branch following our branch naming convention.
[ ] Publish a WIP implementation to Github as a draft PR and ask for feedback.
[ ] Make sure you have implemented tests following the guidelines in: "The good: Test".
[ ] Update the cookbook with examples and showcases.

Review

Once the issue has been implemented and is ready for review:

[ ] Do a self-review.
[ ] Create a pull-request. If you created a draft PR during implementation you can just mark that as "ready for review".

kirbydesign / designsystem