Add tasks for all the new languages

Task/SHA-256/Nim/sha-256.nim

@@ -0,0 +1,13 @@
+import strutils
+
+const SHA256Len = 32
+
+proc SHA256(d: cstring, n: culong, md: cstring = nil): cstring {.cdecl, dynlib: "libssl.so", importc.}
+
+proc SHA256(s: string): string =
+  result = ""
+  let s = SHA256(s.cstring, s.len.culong)
+  for i in 0 .. < SHA256Len:
+    result.add s[i].BiggestInt.toHex(2).toLower
+
+echo SHA256("Rosetta code")