This function gets the value of the specified key from a util/map/hashmap. If the key doesn't exist, return undef.
Since: 3.0
Parameters
map: The original map.key: The specified key.eq: A equality function. If it's ignored, use==to compare elements.hash: A hash function. If it's ignored, convert each element to a string and hash it.
Examples
use <util/map/hashmap.scad>
use <util/map/hashmap_get.scad>
m = hashmap([["k1", 10], ["k2", 20], ["k3", 30]]);
assert(hashmap_get(m, "k2") == 20);

