Duplo compatible Rope Bridge Endpoint

Replacement to fix jungle bridge

Used the the following DIMENSIONAL PARAMETERS according MellyButton February 24, 2021:
d=3.12; // width of internal ridges
rcyl=6.625; // radius of internal cylinder
posstud=8; // stud position
rstud=4.8; // stud outer radius
$fn=90;

Changed **module stud** to:
```
translate(v=[x,y,1.875+z]){
difference(){
/* FIX: shrink top, height was 3.75 */
union() {
studHeightTop=1.75;
studHeightBottom=2;
translate([0,0,studHeightTop/2]) cylinder(h=studHeightTop, r1=r, r2=r-0.5, center=true);
translate([0,0,-studHeightBottom/2]) cylinder(h=studHeightBottom, r=r, center=true);
}
cylinder(h=4, r=r-1.5, center=true);
}
}
```

Support is **necessary** below the attached nose.