Add RPi Pico support

[bog-dan-ro]

Fix a few code style issues in the process

[NuclearPhoenixx]

The Raspberry Pico is easily more than capable of handling a full-blown SSD1306 library like the Adafruit one. Why do you need support here? This is more targeted at the ATTiny series of MCUs like the name suggests, which have very limited RAM. Hence the need for a special library. 🤔

[bog-dan-ro]

There are a few reasons:

• first and foremost, I really like this library :-)
• even it has plenty of ram, I need it for other things
• last but not least, I really like this library ;-)