updated readme with env variables

README.md

@@ -31,6 +31,20 @@ docker pull grocy/grocy-docker:grocy
 
 Or just `docker-compose pull`.
 
+### Environmental variables:
+
+As of grocy v.1.24.1, ENV variables are accessible via the `docker-compose.yml` file as long as they are prefixed by `GROCY_`. For example, to change the language from english to french, you can modify
+
+```
+GROCY_CULTURE: en
+```
+
+to
+
+```
+GROCY_CULTURE: fr
+```
+
 ### To build from scratch
 
 ```
@@ -42,4 +56,4 @@ docker-compose build
 The docker images build are based on [Alpine](https://hub.docker.com/_/alpine/), with an extremelly low footprint (less than 10 MB for nginx, and less than 70MB for grocy with php-fm. That number is eventually bumped up to 353MB after all the dependencies are downloaded, however). 
 
 ## License
-The MIT License (MIT)
+The MIT License (MIT)