Add heroku deployment support

Author: niranjan94

app.json

@@ -0,0 +1,10 @@
+{
+  "name": "Open Event Frontend",
+  "description": "Frontend for Open Event Server",
+  "repository": "https://github.com/fossasia/open-event-frontend",
+  "logo": "https://heroku-www-files.s3.amazonaws.com/getting-started/ember.svg",
+  "keywords": ["ember.js", "static", "open event"],
+  "buildpacks": [
+    { "url": "https://codon-buildpacks.s3.amazonaws.com/buildpacks/heroku/emberjs.tgz" }
+  ]
+}