Add tasks for all the new languages

Task/Run-length-encoding/Nim/run-length-encoding.nim

@@ -0,0 +1,26 @@
+import strutils
+
+type RunLength = tuple[c: char, n: int]
+
+proc encode(inp): seq[RunLength] =
+  result = @[]
+  var count = 1
+  var prev: char
+
+  for c in inp:
+    if c != prev:
+      if prev != chr(0):
+        result.add((prev,count))
+      count = 1
+      prev = c
+    else:
+      inc(count)
+  result.add((prev,count))
+
+proc decode(lst: openarray[RunLength]): string =
+  result = ""
+  for x in lst:
+    result.add(repeatChar(x.n, x.c))
+
+echo encode("aaaaahhhhhhmmmmmmmuiiiiiiiaaaaaa")
+echo decode([('a', 5), ('h', 6), ('m', 7), ('u', 1), ('i', 7), ('a', 6)])