GREG-82: Style tabs

Adding two buttons to a component that can be reused in the sponsor flow.

One links to the front page and the other to the registation page.

frontend/src/routes/components/sponsorGuestButtons.tsx

@@ -3,7 +3,7 @@ import { Box, IconButton, Theme } from '@mui/material'
 import PersonAddIcon from '@mui/icons-material/PersonAdd'
 import React from 'react'
 import { useTranslation } from 'react-i18next'
-import { Link, useHistory } from 'react-router-dom'
+import { useHistory } from 'react-router-dom'
 
 interface SponsorGuestButtonsProps {
   yourGuestsActive?: boolean,