Add env.example file with CMS configuration variables

Author: TRomesh

templates/alloy-template/env.example

@@ -0,0 +1,16 @@
+# Key to fetch content from the CMS.
+# To get the key go to your CMS instance > Settings > API Keys
+OPTIMIZELY_GRAPH_SINGLE_KEY='<SECRET>'
+
+# Client ID and Secret from your CMS instance
+# Go to your CMS instance > Settings > API Keys and click "Create API key"
+OPTIMIZELY_CMS_CLIENT_ID=
+OPTIMIZELY_CMS_CLIENT_SECRET=
+
+# Root CMS instance. For example "https://<something>.cms.optimizely.com"
+OPTIMIZELY_CMS_HOST=
+# From here, all environmental variables are optional
+#
+# Endpoint of GraphQL. Use this variable if you use a non-production instance or a different version
+# OPTIMIZELY_GRAPH_URL=https://cg.optimizely.com/content/v2
+#