Import YEEP-144 library 1.2 sources

Source-only snapshot of the 1.2 release. Drivers/ (the vendored ST HAL and
CMSIS) is excluded at 173 MB; fetch it from STMicroelectronics/STM32CubeH5 to
build.

YEEP144lib/include/YEEP144_I2C.h

@@ -0,0 +1,13 @@
+#ifndef __YEEP144_I2C_H
+#define __YEEP144_I2C_H
+
+#include "stm32h5xx_hal.h"
+
+#define I2C_MUX_ADDR 0xEE
+
+extern I2C_HandleTypeDef hi2c2;
+
+void YEEP144_I2C_Init(void);
+void YEEP144_I2C_MuxSelect(uint8_t busNumber);
+
+#endif