[📖] Add Accordion keyframes docs to /styled/accordion

[maiieul]

Same as in https://qwikui.com/docs/styled/install/

     keyframes: {
        'collapsible-down': {
          from: { height: '0' },
          to: { height: 'var(--qwikui-collapsible-content-height)' },
        },
        'collapsible-up': {
          from: { height: 'var(--qwikui-collapsible-content-height)' },
          to: { height: '0' },
        },
      },