docker-compose.yml: share inventaire files with nginx through a named volume

as using a host path seems to result in that path being empty o_O
Possibly has to do with https://forums.docker.com/t/docker-volume-deleting-content-from-container-when-started/28168

docker-compose.yml

@@ -11,7 +11,7 @@ services:
       - elasticsearch
     # Uncomment if you want to access the code:
     volumes:
-      - ./inventaire/server:/opt/inventaire
+      - inventaire-server:/opt/inventaire
     logging:
       options:
         max-size: "10m"
@@ -56,7 +56,7 @@ services:
     volumes:
       - ./nginx/templates:/etc/nginx/templates/
       - ./nginx/snippets:/etc/nginx/snippets
-      - ./inventaire/server:/opt/inventaire
+      - inventaire-server:/opt/inventaire
       - certbot-www:/var/www/certbot
       - ./certbot/conf:/etc/letsencrypt
     env_file: .env
@@ -78,3 +78,4 @@ volumes:
   couchdb:
   elasticsearch:
   certbot-www:
+  inventaire-server: