Added in a .env.example file.

Signed-off-by: Cliff Hill <xlorep@darkhelm.org>

backend/.env

@@ -1,5 +1,5 @@
 POSTGRES_USER=user
 POSTGRES_PASSWORD=password
 POSTGRES_DB=mydb
-POSTGRES_HOST=postgres
+POSTGRES_HOST=localhost
 POSTGRES_PORT=5432

compose.yml

@@ -9,6 +9,7 @@ services:
       - "8000:8000"
     environment:
       ENVIRONMENT: production
+      POSTGRES_HOST: postgres
     depends_on:
       postgres:
         condition: service_healthy