Dust sensor case (@airrohr) M3 only

I modified the holes to be M3 only, because that's what I have and what I like to use.
The NodeMCU might require to enlarge the holes a little bit with a drill, but I tried and you can also use M3 as is.
In my case, I didn't want to have a loose-jumper cables-setup so I chose to put some headers on a piece of perfboard and use the cable that came with the SDS011 so it's plug-and-play, more error-resistant (no cables falling out or something) while still not requiring soldering the ESP board