Add tasks for all the new languages

Task/Quickselect-algorithm/Sidef/quickselect-algorithm.sidef

@@ -0,0 +1,14 @@
+func quickselect(a, k) {
+    var pivot = a.pick;
+    var left  = a.grep{|i| i < pivot};
+    var right = a.grep{|i| i > pivot};
+
+    given(var l = left.len) {
+        when (k)     { pivot }
+        case (k < l) { __FUNC__(left, k) }
+        default      { __FUNC__(right, k - l - 1) }
+    }
+}
+
+var v = [9, 8, 7, 6, 5, 0, 1, 2, 3, 4];
+say v.range.map{|i| quickselect(v, i)};