Add tasks for all the new languages

Task/Balanced-brackets/Nim/balanced-brackets.nim

@@ -0,0 +1,30 @@
+import random
+randomize()
+
+proc shuffle(s: var string) =
+  for i in countdown(s.high, 0):
+    swap(s[i], s[random(s.len)])
+
+proc gen(n: int): string =
+  result = newString(2 * n)
+  for i in 0 .. <n:
+    result[i] = '['
+  for i in n .. <(2*n):
+    result[i] = ']'
+  shuffle(result)
+
+proc balanced(txt: string): bool =
+  var b = 0
+  for c in txt:
+    case c
+    of '[':
+      inc(b)
+    of ']':
+      dec(b)
+      if b < 0: return false
+    else: discard
+  b == 0
+
+for n in 0..9:
+  let s = gen(n)
+  echo "'", s, "' is ", (if balanced(s): "balanced" else: "not balanced")