docker: add Dockerfile, docker-compose for postgres

devops/docker/Dockerfile

+from fpco/stack-build:lts-12.26
+
+RUN apt-get update && \
+    apt-get install -y git libigraph0-dev && \
+    rm -rf /var/lib/apt/lists/*
+
+RUN mkdir -v /deps && \
+    cd /deps && \
+    git clone https://gitlab.iscpif.fr/gargantext/clustering-louvain-cplusplus && \
+    cd clustering-louvain-cplusplus && \
+    ./install

devops/docker/docker-compose.yaml

+version: '3'
+
+services:
+  postgres:
+    image: 'postgres:latest'
+    ports:
+      - 5432:5432
+    environment:
+      POSTGRES_USER: gargantua
+      POSTGRES_PASSWORD: C8kdcUrAQy66U
+      POSTGRES_DB: gargandbV5
+    volumes:
+      - pgdata:/var/lib/postgresql/data
+      - ../:/gargantext
+      - ../dbs:/dbs
+
+volumes:
+  pgdata: