feat: implement most of enumeration

feat: receive setup packets

feat: implement simple control usb read, writes

wip: usb

chore: some renames

fix: into_alternate choose alternate mode

feat: rewrite main to use types

feat: add registers, pin, exti, usb_device skeleton

feat: add support for newlib

feat: toggle led on exti interrupt push button

feat: use cmsis for register definitions

Initial commit (template)