feat: Support nested children in JSX

[FrederikBolding]

Support nested children in JSX, allowing for UIs to be created like:

<Box>
  <Text>Hello</Text>
  {[1, 2, 3].map((value) => (
    <Text>{value.toString()}</Text>
  ))}
  <Text>World</Text>
</Box>

We flatten the children array in getJsxChildren, which should be used in the client implementation to handle this additional complexity.

[Mrtenz]

This is redundant.

Suggested change

	export type MaybeArray<Type> = Type | Type[] | Nestable<Type>;
	export type MaybeArray<Type> = Nestable<Type>;

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.34%. Comparing base (504e4fd) to head (25318a8).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2482   +/-   ##
=======================================
  Coverage   94.34%   94.34%           
=======================================
  Files         439      439           
  Lines        9053     9057    +4     
  Branches     1392     1392           
=======================================
+ Hits         8541     8545    +4     
  Misses        512      512           

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