Add OLED I2C display example

[kholia]

This PR add an OLED I2C display example.

This example was tested on the following board with ATtiny13 inserted.

This board image is taken from https://www.iot-experiments.com/attiny85-development-board/ for reference purposes.

I used a 0.96" OLED Display Module for testing this code.

This example is based on the excellent https://github.com/wagiminator/ATtiny13-TinyOLEDdemo repository.

Resource usage:

Sketch uses 894 bytes (87%) of program storage space. Maximum is 1024 bytes.
Global variables use 5 bytes (7%) of dynamic memory, ... Maximum is 64 bytes.