Add tasks for all the new languages

Task/Collections/Sidef/collections-3.sidef

@@ -0,0 +1,14 @@
+# create a simple pair
+var p = Pair('a', 'b')
+say p.first;            #=> 'a'
+say p.second;           #=> 'b'
+
+# create a pair of pairs
+var pair = 'foo':'bar':'baz':();   # => Pair('foo', Pair('bar', Pair('baz', nil)))
+
+# iterate over the values of a pair of pairs
+loop {
+    say pair.first;                #=> 'foo', 'bar', 'baz'
+    pair = pair.second;
+    pair == nil && break;
+}