added the "hello world" pd patch file

hello-world/pd/patch.pd

@@ -0,0 +1,5 @@
+#N canvas 827 239 734 565 12;
+#X obj 226 158 osc~ 440;
+#X obj 226 223 dac~;
+#X connect 0 0 1 0;
+#X connect 0 0 1 1;