Update docs for heroku

README.md

@@ -61,3 +61,16 @@ By default, the docker image tag is "latest". Click Deploy to upgrade to the lat
 # Deploy on Heroku
 
 [![Deploy](https://www.herokucdn.com/deploy/button.svg)](https://heroku.com/deploy?template=https://github.com/burke-software/GlitchTip)
+
+1. Deploy the app by clicking the above link and following the prompt.
+2. SECRET_KEY is generated for you. Other environment variables must be entered in the app's settings. See configuration [docs](https://glitchtip.com/documentation/install#Configuration).
+
+## Production considerations
+
+Consider upgrading your Postgres and web dyno plan for production usage.
+
+Most users do not need additional workers. However if you do, create a third dyno typed called extra_worker. Set the run command to `./bin/run-celery.sh`. Do not increase the "worker" dyno count because this these run with an embedded Celery beat scheduler.
+
+## Upgrading GlitchTip
+
+By default, the docker image tag is "latest". Click Deploy to upgrade to the latest GlitchTip docker image.