Megadropdown focus issue on space key (desktop & mobile)

[alionazherdetska]

Description:
The megadropdown fails to jump to the first item after opening when using the Space key. This behavior is observed on both desktop and mobile devices. The expected behavior is that the first item should receive focus immediately upon opening the dropdown, as it does when the Enter key is used.

Steps to Reproduce:
Navigate to the megadropdown component.
Open the dropdown using the Space key.
Observe that the focus does not jump to the first item inside the megadropdown.