docs: document how pre-deploy ci commands might work

Author: josegonzalez

README.md

@@ -75,3 +75,4 @@ For simplicity, each example is standalone, but may be combined as necessary to
 - [Verbose Push Logging](/example-workflows/verbose-logging.yml): Verbose client-side logging may be enabled with this method. Note that this does not enable trace mode on the deploy, and simply tells the `git` client to enable verbose log output
 - [Force Pushing](/example-workflows/force-push.yml): If the remote app has been previously pushed manually from a location other than CI, it may be necessary to enable force pushing to avoid git errors.
 - [Review Apps](/example-workflows/review-app.yml): Handles creation and deletion of review apps through use of `dokku apps:clone` and `dokku apps:destroy`. Review apps are a great way to allow folks to preview pull request changes before they get merged to production.
+  - Placing a shell script at `bin/ci-pre-deploy` can be used to reconfigure the app, as shown in [this example](/example-workflows/review-app/ci-pre-deploy).

example-workflows/review-app/ci-pre-deploy

@@ -0,0 +1,5 @@
+#!/bin/sh -l
+if [ "$IS_REVIEW_APP" = "true" ]; then
+  ssh "$SSH_REMOTE" -- config:set "$APP_NAME" "DOMAIN=$APP_NAME.dokku.me"
+  echo "configured the review app domain"
+fi