fix: db host desambiguation with container name

docker-compose.yml

@@ -31,7 +31,7 @@ services:
     volumes:
       - ./webroot:/var/www/html
     environment:
-      WORDPRESS_DB_HOST:      db
+      WORDPRESS_DB_HOST:      ${WPSTACK_PROJECT_NAME:-wpstack}-db
       WORDPRESS_DB_USER:      ${DB_USER}
       WORDPRESS_DB_NAME:      ${DB_NAME}
       WORDPRESS_DB_PASSWORD:  ${DB_PASS}