README: Add more info on changing memory allocation (#9)

README.md

@@ -16,7 +16,13 @@ You can access the Elasticsearch server directly from the host for debugging pur
 
 ## Memory Limit
 
-This configuration limits memory usage to 512mb. This should be enough for most projects, but if your `elasticsearch` service stops with no obvious reason, increase your docker max memory and/or the service max memory via the `      - "ES_JAVA_OPTS=-Xms512m -Xmx512m"` environment variable in `docker-compose.elasticsearch.yaml`.
+This configuration limits memory usage to 512mb. This should be enough for most projects, but if your `elasticsearch` service stops with no obvious reason, increase your docker max memory and/or the service max memory via the ES_JAVA_OPTS variable:
+
+```yaml
+- "ES_JAVA_OPTS=-Xms512m -Xmx512m"` environment variable in `docker-compose.elasticsearch.yaml`
+```
+
+If you change this variable, make sure to remove the `#ddev-generated` line at the top of the file. 
 
 You can use `ddev logs -s elasticsearch` to investigate what the elasticsearch daemon has been up to, or if you have a RAM-related crash.