build(compose): define application stack

docker-compose.yml

+---
+version: "3.5"
+
+volumes:
+  data: {}
+
+services:
+  ingress:
+    image: nginx:1.21.3-alpine
+    volumes:
+      - type: bind
+        source: ./conf/nginx.conf
+        target: /etc/nginx/nginx.conf
+        read_only: true
+    ports:
+      - ${cd_ingress_port:-8080}:8080
+
+  db:
+    image: docker.gitlab.gwdg.de/sepia/hannaharendt/commentary-backend/commentary-backend:7f150f49
+    volumes:
+      - data:/exist/data
+
+  front:
+    image: docker.gitlab.gwdg.de/sepia/hannaharendt/commentary-frontend/commentary-frontend:034c73cd