wip: feat: Add row--4-cols-medium grid row

[jmuzina]

Done

• Adds a new prop for the Row component, allowing the user to use the new grid row with 4 columns on medium. This will be the new default grid row starting in Vanilla v5. See Vanilla PR 5352 for more.
• Note that this will not build until Vanilla 4.17.0 is released, as the feature is still in review on the Vanilla side.

QA

Storybook

To see rendered examples of all react-components, run:

yarn start

QA in your project

from react-components run:

yarn build
npm pack

Install the resulting tarball in your project with:

yarn add <path-to-tarball>

QA steps

• Navigate to default grid row story.
• See that it has the default "row" class and has 6 columns on the medium breakpoint.
• Navigate to the 4 column medium grid row story.
• See that it has the new "row--4-cols-medium" class and has 4 columns on the medium breakpoint.

Percy steps

• Adds a new story: "Four column medium grid".
• Updates the children of the existing default row story to show an example grid row, rather than just "children..."

[webteam-app]

Demo

Jenkins

demos.haus

[jmuzina]

Closing to re-open a new PR that covers the new grid