Add tasks for all the new languages

Task/Permutations-by-swapping/Sidef/permutations-by-swapping.sidef

@@ -0,0 +1,22 @@
+func perms(n) {
+   var perms = [[+1]]
+   n.times { |x|
+      var sign = -1;
+      perms = gather {
+        for s,*p in perms {
+          var r = (0 .. p.len);
+          take((s < 0 ? r : r.flip).map {|i|
+            [sign *= -1, p[0..i-1], x, p[i..p.end]]
+          }...)
+        }
+      }
+   }
+   perms;
+}
+
+var n = 4;
+for p in perms(n) {
+    var s = p.shift
+    s > 0 && (s = '+1')
+    say "#{p} => #{s}"
+}