esp32/boards: Add LOLIN_S2_MINI ESP32-S2 board.

To support Lolin S2 Mini ESP32-S2 Variant board.  More information about
this board can be found at https://www.wemos.cc/en/latest/s2/s2_mini.html

ports/esp32/boards/LOLIN_S2_MINI/manifest.py

+include("$(PORT_DIR)/boards/manifest.py")
+freeze("./modules")

ports/esp32/boards/LOLIN_S2_MINI/modules/s2mini.py

+# LOLIN S2 MINI MicroPython Helper Library
+
+from micropython import const
+from machine import Pin
+
+# Pin Assignments
+
+# SPI
+SPI_MOSI = const(11)
+SPI_MISO = const(9)
+SPI_CLK = const(7)
+
+# I2C
+I2C_SDA = const(33)
+I2C_SCL = const(35)
+
+# DAC
+DAC1 = const(17)
+DAC2 = const(18)
+
+# LED
+LED = const(15)
+
+# BUTTON
+BUTTON = const(0)
+
+# Helper methods for built in sensors
+
+led = Pin(LED, Pin.OUT, value=0)
+
+button = Pin(BUTTON, Pin.IN, Pin.PULL_UP)

ports/esp32/boards/LOLIN_S2_MINI/mpconfigboard.cmake

+set(IDF_TARGET esp32s2)
+
+set(SDKCONFIG_DEFAULTS
+    boards/sdkconfig.base
+    boards/sdkconfig.spiram_sx
+    boards/sdkconfig.usb
+)
+
+if(NOT MICROPY_FROZEN_MANIFEST)
+    set(MICROPY_FROZEN_MANIFEST ${MICROPY_BOARD_DIR}/manifest.py)
+endif()

ports/esp32/boards/LOLIN_S2_MINI/mpconfigboard.h

+#define MICROPY_HW_BOARD_NAME               "LOLIN_S2_MINI"
+#define MICROPY_HW_MCU_NAME                 "ESP32-S2FN4R2"
+
+#define MICROPY_PY_BLUETOOTH                (0)
+#define MICROPY_HW_ENABLE_SDCARD            (0)
+
+#define MICROPY_HW_I2C0_SCL                 (35)
+#define MICROPY_HW_I2C0_SDA                 (33)
+
+#define MICROPY_HW_SPI1_MOSI                (11)
+#define MICROPY_HW_SPI1_MISO                (9)
+#define MICROPY_HW_SPI1_SCK                 (7)

ports/esp32/boards/LOLIN_S2_MINI/sdkconfig.board

+CONFIG_FLASHMODE_QIO=y
+CONFIG_ESPTOOLPY_FLASHFREQ_80M=y
+CONFIG_USB_AND_UART=y
+# LWIP
+CONFIG_LWIP_LOCAL_HOSTNAME="LOLIN_S2_MINI"
+# end of LWIP