Add an even simpler standalone example.

examples/hello_mojo/hello_mojo.mojom

Index: examples/hello_mojo/hello_mojo.mojom
diff --git a/fusl/test/vector.cc b/examples/hello_mojo/hello_mojo.mojom
similarity index 57%
copy from fusl/test/vector.cc
copy to examples/hello_mojo/hello_mojo.mojom
index 77b04a305215b38c1acde7d693940283fbaefb0a..7c02852bd8bac4bcda8d0306e643deb7d8aa6007 100644
--- a/fusl/test/vector.cc
+++ b/examples/hello_mojo/hello_mojo.mojom
@@ -2,8 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include <vector>
+module examples;
 
-int main(int argc, char** argv) {
-  std::vector<int> xs(10);
-}
+[ServiceName="examples.HelloMojo"]
+interface HelloMojo {
+  Say(string request) => (string response);
+};