ADD documentation about environment variables

Author: ndelangen

.vscode/settings.json

@@ -1,3 +1,8 @@
 {
-  "deepscan.enable": true
+  "deepscan.enable": true,
+  "cSpell.words": [
+    "hichroma",
+    "opensource",
+    "rebased"
+  ]
 }

README.md

@@ -86,6 +86,10 @@ These options are not required, this CLI is 0-config if you have a `build-storyb
 --debug  Output more debugging information
 ```
 
+### Environment variables
+
+This package will load any variables from a `.env` file if present
+
 ## Contributing
 
 Because of the nature of this package: it being a connector between storybook and a web service, you may need an app_code to test this locally. Just send us a message at opensource@hichroma.com or sign up for an account!