Ensure that `RevealGroup` and `RevealContainer` are work together

[RusinovAnton]

Allow:

<RevealContainer interval={300}>
  <RevealGroup interval={300}>
    <Reveal>...</Reveal>
    <Reveal>...</Reveal>
    <Reveal>...</Reveal>
  </RevealGroup>
</RevealContainer>

Disallow?:

<RevealGroup interval={300}>
  <RevealContainer interval={300}>
    <Reveal>...</Reveal>
    <Reveal>...</Reveal>
    <Reveal>...</Reveal>
  </RevealContainer>
</RevealGroup>