adding in ada example

Author: Ian Eyberg

ada/README.md

@@ -0,0 +1,9 @@
+Ada Hello World
+================
+
+This example shows you how you can run your Ada programs as
+unikernels.
+
+```
+gnatmake hello.adb
+```

ada/hello.adb

@@ -0,0 +1,5 @@
+with Ada.Text_IO; use Ada.Text_IO;
+procedure Hello is
+begin
+   Put_Line ("hello from nanos!");
+end Hello;