OLED display lib

[mhaack]

This project is indeed very interesting. Why does it use
https://github.com/euphi/esp8266-oled-ssd1306.git instead of the lib from the platform.io repository?

[luebbe]

Because @euphi has introduced very interesting intermediate classes for DisplayFrame and DisplayOverlay that don't require the

const DisplayNode *self = static_cast<DisplayNode *>(state->userData);

acrobatics like in your DisplayNode.cpp anymore. I first started with your code, but it became to cumbersome for me to add more nodes and different frames, so I continued to search and came across euphis fork. I derived my classes from his.