Add support for ESP32

Conflicts:
	Adafruit_SSD1306.cpp
	Adafruit_SSD1306.h

…transactions & more

removed #define WHITE (&& BLACK && INVERSE)
replaced with class scoped   enum SSD1306_Colors { BLACK=0, WHITE=1, INVERSE=2 };

Namespace issues: #define BLACK conflicts - fixes adafruit#146

Fixes arduino/Arduino#9345

Don't define HAVE_PORTREG for mbed target

adafruit#155

fix build for arduino version < 157

Same bits as before, but now directly visible as nice grid of 0s and 1s..
Include bitmaps and codegen script that generate splash.h.

splash.h: use binary literals for bitmaps

In begin(), there is code to compute the correct contrast value, based on the configuration of the display.
The same code also computes the comPin setting. This code has been factored so that these two values
are computed, and contrast saved in an instance variable.

Later, in dim(), the saved computed contrast value is used when un-dimming the display.

save correct contrast setting for use in dim() function

At least some of the SSD1309 displays can work with this library if SPI_MODE0 is changed to SPI_MODE3.

Instead of allowing the main constructor to do this, we pulled the spiSettings member out to be protected instead of private.  This allows us to create a smple subclass of this code base to run on these displays.  With this I have a version of the ssd1306_128x64_spi sketch that has the subclass code:
```
class Adafruit_SSD1309_SPI : public Adafruit_SSD1306 {
 public:
  Adafruit_SSD1309_SPI(uint8_t w, uint8_t h, SPIClass *spi,
    int8_t dc_pin, int8_t rst_pin, int8_t cs_pin, uint32_t bitrate=8000000UL) :
    Adafruit_SSD1306(w, h, spi, dc_pin, rst_pin, cs_pin, bitrate) {
#ifdef SPI_HAS_TRANSACTION
  spiSettings = SPISettings(bitrate, MSBFIRST, SPI_MODE3);
#endif

    }
};
```
and then I used the hardware version of the constructor:
```
#define OLED_DC     6
#define OLED_CS     7
#define OLED_RESET  8
Adafruit_SSD1309_SPI display(SCREEN_WIDTH, SCREEN_HEIGHT,
  &SPI, OLED_DC, OLED_RESET, OLED_CS);
```
And it now runs on this display

Allow a sketch to sub-class the SSD1306 object and change SPI settings

Fix comment of 128x64 example

Moved repository to github actions

Replace boolean with standard bool

Add support for Particle MCUs' I2C buffer sizing

…his library is going to get refactored anyways and all this code will move out)

To help users getting started less painful. You find 1000 pics of arduino UNOs connected at pins A4, A5 to the display but it doesn't work on your MEGA 2560 because there it's the pins 20, 21 that are used for I2C. You don't necessarily know that already at the moment you start with these displays. And you maybe do not search in the Wire-library for the solution.

Added comments for pins used on different boards

#define SCREEN_ADDRESS instead of hard-coded value

I2C connections for ESP8266:
SCL = GPIO5
SDA = GPIO4
RST = GPIO0

…an 128 segments wide.

Bug was visible when scrolling.
TDB: allow drawing outside visible area to exploit full 128 horizontal resolution in hardware scrolling.

…plash3.png and updating Makefile. Not regenerating splash.h yet.