feature: GPS support on HeltecV3

GPS support via EnvironmentSensorManager. Connect GPS RX to pin 45, TX to pin 46.
Note that while you can disable using the GPS there is no way to power down the GPS without using a mosfet and adjusting PIN_GPS_EN.

variants/heltec_v3/platformio.ini

@@ -21,6 +21,10 @@ build_flags =
   -D ENV_INCLUDE_BME280=1
   -D ENV_INCLUDE_INA3221=1
   -D ENV_INCLUDE_INA219=1  
+  -D ENV_INCLUDE_GPS=1
+  -D PIN_GPS_RX=45
+  -D PIN_GPS_TX=46
+  -D PIN_GPS_EN=-1
 build_src_filter = ${esp32_base.build_src_filter}
   +<../variants/heltec_v3>
   +<helpers/sensors>    
@@ -30,7 +34,8 @@ lib_deps =
   adafruit/Adafruit INA3221 Library @ ^1.0.1
   adafruit/Adafruit INA219 @ ^1.2.3
   adafruit/Adafruit AHTX0 @ ^2.0.5
-  adafruit/Adafruit BME280 Library @ ^2.3.0    
+  adafruit/Adafruit BME280 Library @ ^2.3.0
+  stevemarple/MicroNMEA @ ^2.0.6
 
 [env:Heltec_v3_repeater]
 extends = Heltec_lora32_v3