creality CR10 ender 2 3 Xbelt align mod/fix

passed a few form posting a few good mods for our printer, so now I have decided to post these fix I noticed was really needed on our printers.

this is intended to make the X belt straight with the 2020 aluminium extrusion, in many cases it tends to rub on the lower part /left of the printer adding an idler near the 20t motor pulley
technically it will also inprove the accuracy on the X axis but I think that it can bee really seen except the axiis is 60-80cm long.

parts needed:
2# m3 x10