add choose

docs/lib2x-choose.md

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+# choose
+
+Choose an element from the given list randomly.
+
+**Since:** 2.5
+
+## Parameters
+
+- `choices` : The list to choose from.
+- `seed` : Random seed value.
+
+## Examples
+
+    use <util/choose.scad>;
+    
+    echo(choose([1, 2, 3, 4]));

src/util/choose.scad

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+/**
+* choose.scad
+*
+* @copyright Justin Lin, 2021
+* @license https://opensource.org/licenses/lgpl-3.0.html
+*
+* @see https://openhome.cc/eGossip/OpenSCAD/lib2x-choose.html
+*
+**/
+
+function choose(choices, seed) =
+    let(c = is_undef(seed) ? rands(0, len(choices) - 1, 1) : rands(0, len(choices) - 1, 1, seed)) 
+    choices[round(c[0])];