boards: add Heltec Wireless Stick V3 (ESP32-S3) board and variant

[AbedKarmi]

Title: Add Heltec Wireless Stick V3 (ESP32-S3) board and variant

What:

• Adds boards/heltec_wireless_stick_v3.json and variants/heltec_wireless_stick_v3/pins_arduino.h.

Why:

• Support Heltec Wireless Stick V3 (ESP32‑S3) in the boards collection so PlatformIO users can select the board by name.

Testing performed:

• Built the LoRa-RX project locally using the same board/variant files and verified pio run -e serial -v completed and produced firmware.bin.

Notes:

• No firmware/source changes included — only board / variant metadata and pin mapping.
• If maintainers prefer different naming or metadata fields, I can update the files.