Add ESP8285 ELRS receiver as board

[xznhj8129]

This pull adds ESP8285-based ExpressLRS receivers as supported boards with, for now, USB companion and Repeater modes. It was tested to function with WSL3 nodes. There's several caveats:

• Due to limited RAM, only 25 contacts are supported. More contacts fill the RAM to cause instability or just cause a build failure.
• The boards.json is taken straight from ELRS and is missing a few things, i could use some help there
• I'm not sure if there's gonna be room for the Wifi companion with that RAM level.
• There is no USB (serial adapter required) or BLE on them

Obviously this is a very limited application but opening the door to using ELRS receivers as nodes will open up a lot of exciting possibilities as most of them cost only a fraction of the cost of usual Lora modules, and the newer ones use ESP32s wich will allow a more fully featured build. Meshtastic does offer ELRS transmitters as board options but receivers can be far more flexible in custom builds due to their smaller footprint.
Corrections welcome, this is the first time i develop using PlatformIO.