added torus_knot

src/torus_knot.scad

@@ -0,0 +1,11 @@
+function torus_knot(p, q, phi_step) = [
+    for(phi = [0:phi_step:6.28318])
+    let(
+        degree = phi * 180 / 3.14159,
+        r = cos(q * degree) + 2,
+        x = r * cos(p * degree),
+        y = r * sin(p * degree),
+        z = -sin(q * degree)
+    )
+    [x, y, z]
+];