added test for hello world

Hello World/config.json

@@ -0,0 +1,11 @@
+{  
+  "name": "Hello world",  
+  "version": "1",  
+  "slug": "hello_world",  
+  "description": "My first real add-on!",  
+  "arch": ["armhf", "armv7", "aarch64", "amd64", "i386"],  
+  "startup": "application",  
+  "boot": "auto",  
+  "options": {},  
+  "schema": {}
+}

Hello World/dockerfile

@@ -0,0 +1,10 @@
+ARG BUILD_FROM
+FROM $BUILD_FROM
+
+ENV LANG C.UTF-8
+
+# Copy data for add-on
+COPY run.sh /RUN 
+chmod a+x /run.sh
+
+CMD [ "/run.sh" ]

Hello World/run.sh

@@ -0,0 +1,3 @@
+#!/usr/bin/with-contenv bashio
+
+echo Hello world!