chore(tests): add readme note about remote host testing

test/README.md

@@ -15,3 +15,15 @@ Edit the messages, usernames or point to a different instance.
 
 1. `npm install`
 1. `node fakeChat.js`
+
+## Public Testing
+
+Run `./test-local.sh` and it'll create a public URL that you can access your local Owncast instance from. This is particularly useful for testing mobile and other external devices, as well as webhooks. Make sure Owncast is running under port 8080.
+
+If you'd like your own custom hostname that uses your username follow the instructions printed, otherwise use auto-generated name printed to the console for testing.
+
+```
+$ ./test/test-local.sh
+Please wait. Making the local server port 8080 available at https://oc-gabek-develop.serveo.net
+Forwarding HTTP traffic from https://oc-gabek-develop.serveo.net
+```