feat(board): Add Ferris 0.2 boards

* Onboard stm32f072 with mcp23018 IO expander.
* No underglow support yet.
* Miryoku inspired default layout.

app/boards/arm/ferris/ferris_rev02_defconfig

@@ -0,0 +1,43 @@
+# SPDX-License-Identifier: MIT
+
+CONFIG_BOARD_FERRIS=y
+CONFIG_SOC_SERIES_STM32F0X=y
+CONFIG_SOC_STM32F072XB=y
+# 48MHz system clock
+CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC=48000000
+
+# enable PINMUX
+CONFIG_PINMUX=y
+
+# enable GPIO
+CONFIG_GPIO=y
+
+# Enable i2c
+CONFIG_I2C=y
+
+# ZMK Settings
+CONFIG_ZMK_USB=y
+CONFIG_ZMK_KSCAN_GPIO_DRIVER=y
+CONFIG_ZMK_KSCAN_COMPOSITE_DRIVER=y
+CONFIG_ZMK_KSCAN_MATRIX_POLLING=y
+CONFIG_USB_SELF_POWERED=n
+
+# Enable IO multiplexer
+CONFIG_GPIO_MCP23017=y
+
+# Needed to reduce this to size that will fit on F072
+CONFIG_HEAP_MEM_POOL_SIZE=1024
+
+# clock configuration
+CONFIG_CLOCK_CONTROL=y
+
+# Clock configuration for Cube Clock control driver
+CONFIG_CLOCK_STM32_SYSCLK_SRC_PLL=y
+# use HSI as PLL input
+CONFIG_CLOCK_STM32_PLL_SRC_HSI=y
+# produce 48MHz clock at PLL output
+# CONFIG_CLOCK_STM32_PLL_PREDIV=1
+CONFIG_CLOCK_STM32_PLL_MULTIPLIER=6
+CONFIG_CLOCK_STM32_AHB_PRESCALER=1
+CONFIG_CLOCK_STM32_APB1_PRESCALER=1
+# CONFIG_CLOCK_STM32_APB2_PRESCALER=1