Add tasks for all the new languages

Task/Longest-common-subsequence/Ring/longest-common-subsequence.ring

@@ -0,0 +1,16 @@
+see longest("1267834", "1224533324") + nl
+
+func longest a, b
+     if a = "" or b = "" return "" ok
+     if right(a, 1) = right(b, 1)
+        lcs = longest(left(a, len(a) - 1), left(b, len(b) - 1)) + right(a, 1)
+        return lcs
+     else
+        x1 = longest(a, left(b, len(b) - 1))
+        x2 = longest(left(a, len(a) - 1), b)
+        if len(x1) > len(x2)
+           lcs = x1
+           return lcs
+        else
+           lcs = x2
+           return lcs ok ok