[MasterDetailLayout] Verify proper usage of Master / Detail wrapper components

[sissbruecker]

Master and detail content should be wrapped into the respective wrapper components to ensure view transitions work properly with React:

<MasterDetailLayout>
  <MasterDetailLayout.Master>...</MasterDetailLayout.Master>
  <MasterDetailLayout.Detail>...</MasterDetailLayout.Detail>
</MasterDetailLayout>

However, that usage is somewhat unusual compared to other components and not discoverable when just writing code in the IDE.

To improve the situation we should:

• Throw an error if any other type of child component is used in MasterDetailLayout
• Improve JS docs for the outer MasterDetailLayout to provide an example of how to provide content to the component