Add tasks for all the new languages

Task/Evolutionary-algorithm/Nim/evolutionary-algorithm.nim

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+import math, os
+randomize()
+
+const
+  target = "METHINKS IT IS LIKE A WEASEL"
+  alphabet = " ABCDEFGHIJLKLMNOPQRSTUVWXYZ"
+  p = 0.05
+  c = 100
+
+proc random(a: string): char = a[random(a.low..a.len)]
+
+proc negFitness(trial): int =
+  for i in 0 .. <trial.len:
+    if target[i] != trial[i]: inc result
+
+proc mutate(parent): string =
+  result = ""
+  for c in parent: result.add if random(1.0) < p: random(alphabet) else: c
+
+var parent = ""
+for i in 1..target.len: parent.add random(alphabet)
+
+var i = 0
+while parent != target:
+  var copies = newSeq[string](c)
+  for i in 0 .. <copies.len: copies[i] = mutate(parent)
+
+  var best = copies[0]
+  for i in 1 .. <copies.len:
+    if negFitness(copies[i]) < negFitness(best): best = copies[i]
+  parent = best
+
+  echo i, " ", parent
+  inc i