add heltec_v4 board.

[Quency-D]

Features of heltec_v4:
1.Equipped with ESP32-S3R2 chip, featuring built-in 2MB PSRAM and external 16MB Flash, making it more suitable for UI and complex system design;
2.SX-1262 LoRa chip, high-power version with LoRa transmission power increased to 27±1dBm;
3.Form factor and pin compatibility with WiFi LoRa 32 V2 and V3;
4.PC casing protects the screen and integrates a 2.4G antenna, enhancing overall durability and integration;
5.Supports Wi-Fi b/g/n, Bluetooth(BLE), and LoRa communication, with a reserved IPEX (U.FL) interface;
6.Supports solar power: Added SH1.25-2P solar interface, compatible with 4.4-6V/540mA solar panel input;
7.Optimized lithium battery management: Supports charge/discharge management, overcharge protection, power level detection, and automatic switching between USB and battery power, with compatibility for solar charging;
8.Added SH1.25-8Pin GPS interface for easy expansion of positioning functionality.
9.Type-C USB interface with integrated voltage regulation, ESD protection, short-circuit protection, and RF isolation design;

🤝 Attestations

• I have tested that my proposed changes behave as described.
• I have tested that my proposed changes do not cause any obvious regressions on the following devices:
  • Heltec (Lora32) V3
  • Heltec (Lora32) V4

[fifieldt]

This looks good to me, but I'd prefer if someone else with more of a clue takes a look at the transmitEnable functiion :)