Anet A8 X-Idler set with tensioner

Another version of X-idler for ANET A8 with integrated tensioner and brackets for M3 nuts.

other upgrades currently installed on my printer:

• Stiff Y- front plate with integrated tensioner:
  https://www.thingiverse.com/thing:2867409

• E3D carriage:
  https://www.thingiverse.com/thing:2278021

• simple spool holder:
  https://www.thingiverse.com/thing:2257054

• z-antiwobble bracket
  https://www.thingiverse.com/thing:2870504

• optional Z limit switch:
  https://www.thingiverse.com/thing:2276782