docs: Note local changes needed to build in Docker

README.md

@@ -39,6 +39,12 @@ To build the code vectors for the ICD-9 codelist for the deployed environment:
 3. Build the image with: `docker build . -t headwayio/medical_transcription`
 4. Run a container with: `docker run --env-file ./.env -p 4000:4000 headwayio/medical_transcription`
 
+### Caveats
+
+You may need to make a few changes to get the app running in Docker at the moment:
+- In `lib/medical_transcription/application.ex`, comment out the `DNSCluster` child spec.
+- In `rel/env.sh.eex`, comment out the `ERL_AFLAGS`, `RELEASE_DISTRIBUTION`, and `RELEASE_NODE` environment variables.
+
 ## Learn more
 
   * Official website: https://www.phoenixframework.org/