[spike] make root optional in container

[itsdouges]

Hey @bbohlender here's a quick spike to test the waters. We'd conditionally render <Root> if it's missing in what we'd consider "top level components".

Should that be all components? If you have a list that should be changed and are happy with the approach I can do it all, add tests, and get it into a mergeable state.

[itsdouges]

We could rename the other hook to useParentOrThrow and this one to useParent. Happy with whatever.

[bbohlender]

@itsdouges thanks for the PR
it's a good start. There are a few open questions for me:

• Root currently has a few special properties (e.g. pixelSize that would need to be present on a Container/Text now or configured through a context further up the tree)
• Root already is a Container so </...></...> is unnecessary
• how can we propagate the idea to vanilla uikit to ensure both have a very similar API

Would love to discuss possible solutions and consolidate ideas to solve these things :)