support SSD1681 eink display in library

[pikot]

hi! I have implemented support to ssd1681 driver, also I added busy line monitoring.

It works for 3 months in my project. I think it can be used in library too.

[olikraus]

I have stopped supporting eink displays. There are other / better libs for eink like https://github.com/ZinggJM

Moreover U8g2_Arduino is just a release project for u8g2 project. Pull request do not make sense here, because the content is generated.

[pikot]

I have project which uses u8g2 and support 2 displays oled sh1106 and eink ssd1681, also it uses tcMenuLib which uses u8g2 lib also, and in my opinion implementation eink-display support in u8g2 is better way then try to use 2 different graphic libraries in one project. I agree - ZinggJMs lib gives now better experience, but eink support in u8g2 gives me now pretty successful experience, and I believe it can be useful for somebody else.

I can commit support ssd1681 into u8g2 directly =) At least I can try.

As I said before, I implemented BUSY pin monitoring instead delay magic, and it gives solidness to code )

[olikraus]

I could offer to mention your project in u8g2 gallery page (https://github.com/olikraus/u8g2/wiki/gallery) if you sent me a picture of your eink display.
I could then refer to https://github.com/pikot/U8g2_Arduino for all those users who want to use the same display.