Add some notes about extra_hosts directive within README_DEV.md (#…

…111)

* Update README_DEV.md

add some notes about `extra_hosts` directive

* add image

README_DEV.md

@@ -7,4 +7,33 @@ Follow instructions are for development environment.
    * set `G3WSUITE_LOCAL_CODE_PATH` with path to your local G3W-SUITE code location.
 
 2. Run `docker compose -f docker-compose-dev.yml up -d`.
-   1. If all went well G3W-SUITE is running in development mode on http://127.0.0.1:8000
+   1. If all went well G3W-SUITE is running in development mode on http://127.0.0.1:8000
+
+
+## Additional notes
+
+If you are working in a mixed setup (ie. a local [postgis](https://postgis.net/) instance + a [g3w-suite-docker](https://github.com/g3w-suite/g3w-suite-docker) container), you should add an `extra_hosts` directive within your `docker-compose-dev.yml` to make your local postgres databases accessible from both sides:
+
+![Connecting to a local postgress DB](https://github.com/g3w-suite/g3w-admin/assets/9614886/ade856d2-99ec-4024-ab0d-7c631cfa67e8)
+
+```yaml
+
+  g3w-suite:
+    image: g3wsuite/g3w-suite:dev
+
+    ...
+
+    extra_hosts:
+      - "postgis16:host-gateway"
+```
+
+taking care to edit your `hosts` file accordingly:
+
+```sh
+# Added for G3W-SUITE docker
+127.0.0.1 postgis16
+```
+
+**For more info:**
+
+- https://docs.docker.com/compose/compose-file/compose-file-v3/#extra_hosts