add pnoise1

src/experimental/_impl/_pnoise1.scad

@@ -0,0 +1,10 @@
+function _pnoise1(x, n, slopes) =
+    let(
+        lo = floor(x),
+        hi = (lo + 1) % n,
+        dist = x - lo,
+        loPos = slopes[lo] * dist,
+        hiPos = -slopes[hi] * (1 - dist),
+        u = pow(dist, 3) * (dist * (dist * 6 - 15) + 10)
+    )
+    loPos * (1 - u) + hiPos * u;