Modal footer: apply correct theme variables for nested elements inside footer

Which issue does this PR close?

This PR fixes an issue where grey buttons (buttons with attentionLevel="3") in an inline footer would not change their color to white, when modal footer has type="inline" An example code snippet of the use would look like this:

<kirby-modal-footer type="inline">
  <button kirby-button attentionLevel="3">Click Me</button>
</kirby-modal-footer>

And the output of this snippet would show a grey button on a grey background when a modal footer is set as inline, which makes the button not stand out:

What is the new behavior?

When the type="inline" is added to a modal footer, the correct theme (light-theme) will be applied causing the grey buttons within the modal footer to properly turn white.

The output will now look like this:

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Are there any additional context?

Checklist:

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

Reminders

[ ] Make sure you have implemented tests following the guidelines in: "The good: Test".
[ ] Make sure you have updated the cookbook with examples and showcases (for bug fixes, enhancements & new components).

Review

[x] Determine if your changes are a fix, feature or breaking-change, and add the matching label to your PR. If it is tooling, dependency updates or similar, add ignore-for-release.
[x] Do a self-review.
[ ] Request that the changes are code-reviewed
[ ] Request that the changes are UX reviewed (only necessary if your PR introduces visual changes)

When the pull request has been approved it will be merged to develop by Team Kirby.

kirbydesign / designsystem