Add FYSETC F6 V1.4

[GerogeFu]

Add to support FYSETC F6 V1.4 . I already Open a PR to update variant https://github.com/platformio/platformio-pkg-framework-arduinoavr/tree/master/variants/fysetcf6 But the platformio-pkg-framework-arduinoavr is read only state , i can't see the progress of the PR. And if you can't see the PR , the variants file is located here https://github.com/GerogeFu/platformio-pkg-framework-arduinoavr/tree/update-fysetc-f6/variants/fysetcf6

[tomekc]

This PR is almost a year old, why hasn't it been merged yet?

[valeros]

https://github.com/platformio/platformio-pkg-framework-arduinoavr repository is archived and no longer relevant. PlatformIO now uses the official Arduino packages for ATMEGA4809 and there is no support for his board https://github.com/arduino/ArduinoCore-megaavr/tree/master/variants