Format HMC5883.md better

Improved formatting and set code blocks to use JS highlighting
Format ADXL345.md better

All code in javascript code blocks, and general formatting improvements.
Format DHT11.md better
Format DHT22.md better
Update DHT22.md with polarity warning

Apparently, if you reverse the polarity, it will fry the sensor (and get really hot really fast); added warning to that effect.
displays
Merge branch 'master' of https://github.com/SpenceKonde/EspruinoDocs into SpenceKonde-master

Conflicts:
	devices/DHT11.md
	devices/DHT22.md
	devices/HMC5883.md