Poll example: add mbed_app.json

Author: mprse

APIs_Platform/Poll/mbed_app.json

@@ -0,0 +1,8 @@
+{
+    "config": {
+        "UART1_TX": "D1",
+        "UART1_RX": "D0",
+        "UART2_TX": "USBTX",
+        "UART2_RX": "USBRX"
+    }
+}