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>    
@@ -31,6 +35,7 @@ lib_deps =
   adafruit/Adafruit INA219 @ ^1.2.3
   adafruit/Adafruit AHTX0 @ ^2.0.5
   adafruit/Adafruit BME280 Library @ ^2.3.0
+  stevemarple/MicroNMEA @ ^2.0.6
 
 [env:Heltec_v3_repeater]
 extends = Heltec_lora32_v3

variants/heltec_v3/target.cpp

@@ -14,7 +14,14 @@ WRAPPER_CLASS radio_driver(radio, board);
 
 ESP32RTCClock fallback_clock;
 AutoDiscoverRTCClock rtc_clock(fallback_clock);
+
+#if ENV_INCLUDE_GPS
+  #include <helpers/sensors/MicroNMEALocationProvider.h>
+  MicroNMEALocationProvider nmea = MicroNMEALocationProvider(Serial1);
+  EnvironmentSensorManager sensors = EnvironmentSensorManager(nmea);
+#else
   EnvironmentSensorManager sensors;
+#endif
 
 #ifdef DISPLAY_CLASS
   DISPLAY_CLASS display;