Selecting button style in SteppedForm (once ported)

[luckylwk]

Added the following first step for the onboard @jonashaefele:

{
    slug: 'hello',
    title: 'Hello!',
    type: 'md',
    actions: [
      // { label: 'I want to learn more', navigate: 'next' },
      { label: 'I want to learn more', navigate: 'goto', slide: 'overview' },
      { label: 'Get started', navigate: 'goto', slide: 'name' }
    ],
    lede: `Lipsum`,
    body: `Lipsum`,
  },

and then realized we can't define styling for the navigate: 'goto' buttons. It will by default become primary when using navigate: 'next'. Something to implement when moving the SteppedForm over to HDS

[jonashaefele]

just add variant: 'primary' or variant: 'subtle to the button. It'll forward the variant key from the action object to the button.