Adding docker-compose and Dockerfile

Dockerfile

+FROM rust:1-buster
+
+RUN set -ex && \
+    apt-get update && \
+    apt-get install -y --no-install-recommends ostree && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists
+
+RUN set -ex && \
+    mkdir -p /repos && \
+    cargo install --git https://github.com/flatpak/flat-manager
+
+WORKDIR /repos
+
+CMD flat-manager
+

docker-compose.yml

+version: "3.7"
+services:
+  db:
+    image: postgres:13.1
+    volumes:
+      - db-data:/var/lib/postgresql/data
+    networks:
+      - backend
+    env_file: .env-postgres
+    restart: unless-stopped
+
+  flat-manager:
+    image: flat-manager
+    environment:
+      REPO_CONFIG: "/config.json"
+    ports:
+      - 127.0.0.1:8080:8080
+    volumes:
+      - flatpak-repo:/repos
+      - ./config.json:/config.json
+    networks:
+      - backend
+      - frontend
+    restart: unless-stopped
+
+networks:
+  frontend:
+  backend:
+    internal: true
+
+volumes:
+  db-data:
+  flatpak-repo: