Get ready for releasing 0.70.0  #779

@MoOx It would be great if we could release a version 0.70.0 with all the latest improvements soon.

If we went JSX 4 only, it would be possible to use "inheritance" for the prop types which would be very nice, but maybe it is too early for that as it will take some time until most people/projects have migrated to JSX 4 (which currently is not even released yet).

So I now believe that we should release a version 0.70.0 with the changes/improvements made so far. #770 will ensure compatibility with JSX 4.

TODO from my point of view:

• 1. Decide on Revert the Platform.os changes? #778.
• 2. Should we leave the deprecations from Adaptations for ReScript 10 / use records with optional fields #769? Or maybe remove them and just allow the old and the new approach (creation function + record with optional fields) side by side for now? And deprecate the old approach in some later version.
• 3. Test with existing projects (JSX 3).
• 4. Test with JSX 4.
• 5. Release Notes / Migration Guide.