Add tasks for all the new languages

Task/Empty-directory/Sidef/empty-directory-1.sidef

@@ -0,0 +1 @@
+Dir.new('/my/dir').is_empty;    # true, false or nil

Task/Empty-directory/Sidef/empty-directory-2.sidef

@@ -0,0 +1,8 @@
+func is_empty(dir) {
+    dir.open(\var dir_h) || return nil;
+    dir_h.each { |file|
+        file ~~ ['.', '..'] && next;
+        return false;
+    };
+    return true;
+};