samples: zephyr: add hello-world

This is a minimal example application that works on various boards,
without target-specific definitions, device tree overlay files, etc.

It's been tested on frdm_k64f, 96b_carbon, and 96b_nitrogen.

Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
diff --git a/samples/zephyr/hello-world/sample.yaml b/samples/zephyr/hello-world/sample.yaml
new file mode 100644
index 0000000..4241778
--- /dev/null
+++ b/samples/zephyr/hello-world/sample.yaml
@@ -0,0 +1,9 @@
+sample:
+  name: Application Skeleton
+  description: Basic "hello world" application, but loadable by mcuboot
+  platforms: all
+tests:
+    - test:
+        build_only: true
+        tags: samples tests
+        min_ram: 16