Slides: Allow slides to have equal height

[troelslenda]

Which issue does this PR close?

This PR closes #3396

What is the new behavior?

Each swiper-slide has the same height in DOM allowing for content of each swiper-slide to extend to a height of 100% solution is based on https://github.com/nolimits4web/swiper/issues/2372#issuecomment-349004052

Does this PR introduce a breaking change?

• [ ] Yes
• [x] No

Are there any additional context?

⚠️ The branch was upstreamed with flag --no-verify

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".
• [x] Make sure you have updated the cookbook with examples and showcases (for bug fixes, enhancements & new components).

Review

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• [x] Do a self-review.
• [x] Request that the changes are code-reviewed
• [x] 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.