fix(accordions): allow dynamic height for stepper content

[Francois-Esquire]

Description

Use a pure CSS implementation to animate/transition height for the active Step in Stepper component. This fixes a bug found with dynamically changing heights in a Stepper.Step, since there are instances where changing the height after the Stepper.Content has been rendered does not change the height.

Detail

There is long-standing issue with animating height change that affects the web, and the implementation here makes use of grid (specifically transitioning the grid-template-rows CSS property) to handle that animation.

This treatment can be applied across the accordions package where this is relevant.

Checklist

• 👌 design updates will be Garden Designer approved (add the designer as a reviewer)
• 🌐 demo is up-to-date (yarn start)
• ⬅️ renders as expected with reversed (RTL) direction
• 🤘 renders as expected with Bedrock CSS (?bedrock)
• 💂‍♂️ includes new unit tests. Maintain existing coverage (always >= 96%)
• ♿ tested for WCAG 2.1 AA accessibility compliance
• 📝 tested in Chrome, Firefox, Safari, and Edge

[coveralls]

coverage: 96.23% (+0.03%) from 96.201% when pulling d9f6945 on mike/fix/stepper-dynamic-height into 13b9ac1 on main.

[geotrev]

Glad this worked and love the simplicity of the approach.