MAX7219 dot matrix docu extended

[sternegugger]

The format is now more readable. Some corrections and better explanations have been made.

[blakadder]

the compile information has to be included at the top of the page as the rest of the sensors see for example https://tasmota.github.io/docs/AHT2x/

[sternegugger]

the compile information has to be included at the top of the page as the rest of the sensors see for example https://tasmota.github.io/docs/AHT2x/

Done with 19eda3f