Add tasks for all the new languages

Task/Quickselect-algorithm/Nim/quickselect-algorithm.nim

@@ -0,0 +1,19 @@
+proc qselect[T](a: var openarray[T]; k: int, inl = 0, inr = -1): T =
+  var r = if inr >= 0: inr else: a.high
+  var st = 0
+  for i in 0 .. < r:
+    if a[i] > a[r]: continue
+    swap a[i], a[st]
+    inc st
+
+  swap a[r], a[st]
+
+  if k == st:  a[st]
+  elif st > k: qselect(a, k, 0, st - 1)
+  else:        qselect(a, k, st, inr)
+
+let x = [9, 8, 7, 6, 5, 0, 1, 2, 3, 4]
+
+for i in 0..9:
+  var y = x
+  echo i, ": ", qselect(y, i)