Add support for Blue Pill Plus board

This is a ST-Microelectronics blue pills's development board clone from WeAct Studio with some extra switchs and a LED in addition to a USB-C port connector.

Detail of the board is here: https://stm32-base.org/boards/STM32F103C8T6-WeAct-Blue-Pill-Plus-Clone.html

I have been testing this board and the LED and ACK button I added are both functional.