Add docker compose to run motion with singularity

Add docker compose to start up Motion with Singularity backing store on
a shared volume.

Fixes #53

docker-compose.yml

@@ -0,0 +1,52 @@
+version: "3"
+
+services:
+  db:
+    image: postgres:15
+    restart: always
+    healthcheck:
+      test: [ "CMD-SHELL", "pg_isready -U postgres" ]
+      interval: 5s
+      timeout: 5s
+      retries: 5
+    environment:
+      POSTGRES_USER: ${SINGULARITY_DB_USER:-postgres}
+      POSTGRES_PASSWORD: ${SINGULARITY_DB_PASSWORD:-postgres}
+      POSTGRES_DB: ${SINGULARITY_DB_NAME:-singularity}
+    volumes:
+      - motion-singularity-volume:/var/lib/postgresql/data
+    ports:
+      - 5432:5432
+
+  singularity_api:
+    image: ghcr.io/data-preservation-programs/singularity:main
+    command: run api --bind :9090
+    ports:
+      - 9090:9090
+    environment:
+      DATABASE_CONNECTION_STRING: postgres://${SINGULARITY_DB_USER:-postgres}:${SINGULARITY_DB_PASSWORD:-postgres}@db:5432/${SINGULARITY_DB_NAME:-singularity}
+    depends_on:
+      db:
+        condition: service_healthy
+
+  singularity_dataset_worker:
+    image: ghcr.io/data-preservation-programs/singularity:main
+    command: run dataset-worker
+    environment:
+      DATABASE_CONNECTION_STRING: postgres://postgres:postgres@db:5432/singularity
+    depends_on:
+      db:
+        condition: service_healthy
+
+  motion:
+    image: ghcr.io/filecoin-project/motion:main
+    entrypoint: motion --experimentalSingularityStore --experimentalRemoteSingularityAPIUrl=http://singularity_api:9090/api
+    ports:
+      - 40080:40080
+    environment:
+      - MOTION_STORE_DIR=/usr/src/app/storage
+    volumes:
+      - motion-singularity-volume:/usr/src/app/storage
+
+volumes:
+  motion-singularity-volume: