Lerdge 2in1-S1 extruder reference

This is a reference model of 2in1-S1 extruders by different vendors such as Bigtreetech, Lerdge, XCR and so on.

It's based on 2in1-v2 model by @darwin-de (see remix source). Provided are STL, STEP and Fusion 360 (f3d) files.

This is S1 model - it has radiator fins on both sides, front and back. It also features through-holes in the heatsink body in the shape of split Y (see rendered back image).

Side slots where heatbreak setscrews are much longer and are on both sides.