Lost AVR Compability

[AVividLight]

Overwriting Arduino main.cpp with custom main.cpp based on SAMD architecture could make AVR-based Arduinos (or others) unable to run glEEmail successfully.

We need to test any version of glEEmail >= alpha 5 with other boards to confirm.

Compatibility was lost in commit d59d34e104a0020d7795292dacd10f3596685ae4

To fix this, maybe add some macro magic, or stop overwriting Arduino main().

[AVividLight]

Ultimately, this isn't a huge thing because glEEmail won't run on a board other than the Nano 33 IoT without code modifications anyway (due to dependence on on-board WiFi). Cross platform support would probably require some abstraction between networking and network access (some of which has already been done).