feat: Add Russell, a board designed to go Up! on a balloon (#9079)

Hardware repository: https://github.com/Meshtastic-Malaysia/russell
- Designed to mount on an ER34615/IFR32700 cell
- RAK3172 STM32WLE5CCU6 MCU + integrated SX1262 LoRa
- CDtop CD-PA1010D GPS
- Bosch Sensortec BME280 sensor
- Consonance CN3158 LiFePO4 solar charger

Signed-off-by: Andrew Yong <me@ndoo.sg>

variants/stm32/russell/platformio.ini

@@ -0,0 +1,21 @@
+; Russell is a board designed to mount on an ER34615/IFR32700 cell and go Up! on a balloon
+; Hardware repository: https://github.com/Meshtastic-Malaysia/russell
+; - RAK3172 STM32WLE5CCU6 MCU + integrated SX1262 LoRa
+; - CDtop CD-PA1010D GPS
+; - Bosch Sensortec BME280 sensor
+; - Consonance CN3158 LiFePO4 solar charger
+[env:russell]
+extends = stm32_base
+board = wiscore_rak3172
+board_level = extra
+board_upload.maximum_size = 233472 ; reserve the last 28KB for filesystem
+build_flags =
+  ${stm32_base.build_flags}
+  -Ivariants/stm32/russell
+  -DPRIVATE_HW
+lib_deps =
+  ${stm32_base.lib_deps}
+	# renovate: datasource=custom.pio depName=Adafruit BME280 packageName=adafruit/library/Adafruit BME280 Library
+	adafruit/Adafruit BME280 Library@2.3.0
+
+upload_port = stlink