Adding STM32CubeU5 package to platformIO registry

[orvalman]

Hi, We are building a custom framework under ststm32 platform for our evaluation kits. Would it be possible to get the following repository added in platformIO registry: https://github.com/STMicroelectronics/STM32CubeU5

Adding this would also make it possible to add support for nucleo_u575zi_q board on stm32cube framework in the future. Thanks!

[tookitogo]

I'd like to see this, too!