title: i can't switch between pages with react-router
body: <p>today i am writing my latest project.
  but i have a problem with react router.
  when i want to switch page from navbar
  it can't.
  here is the demo &gt;&gt; <a href="https://zedjf.csb.app/" rel="nofollow noreferrer">https://zedjf.csb.app/</a>
  if you can pls help me solve this problem, any suggestion will be very helpful to improve my project.
  thnx.</p>
  <blockquote>
  <p>github code: <a href="https://github.com/ennouri0maak/forslack" rel="nofollow noreferrer">https://github.com/ennouri0maak/forslack</a></p>
  </blockquote>