Add tasks for all the new languages

Task/Singleton/Sidef/singleton.sidef

@@ -0,0 +1,21 @@
+class Singleton(name) {
+    static instance;
+
+    method new(name) {
+        instance := Singleton.bless(Hash(:name => name));
+    }
+    method new {
+        Singleton.new(nil);
+    }
+}
+
+var s1 = Singleton('foo');
+say s1.name;                #=> 'foo'
+say s1.object_id;           #=> '30424504'
+
+var s2 = Singleton();
+say s2.name;                #=> 'foo'
+say s2.object_id;           #=> '30424504'
+
+s2.name = 'bar';            # change name in s2
+say s1.name;                #=> 'bar'