Very minimal doc for Docker install

docs/docker.md

@@ -0,0 +1,33 @@
+# Docker
+
+There is now an official [uMap](https://hub.docker.com/r/umap/umap) image.
+
+To run it with docker compose, use a `docker-compose.yml` like this:
+
+```yaml
+version: '3'
+services:
+  db:
+    image: postgis/postgis:14-3.3-alpine
+    environment:
+      - POSTGRES_HOST_AUTH_METHOD=trust
+    volumes:
+      - db:/var/lib/postgresql/data
+
+  app:
+    image: umap/umap:x.x.x
+    ports:
+      - "8001:8000"
+    environment:
+      - DATABASE_URL=postgis://postgres@db/postgres
+      - SECRET_KEY=some-long-and-weirdly-unrandom-secret-key
+      - SITE_URL=https://umap.local/
+      - UMAP_ALLOW_ANONYMOUS=True
+      - DEBUG=1
+    volumes:
+      - data:/srv/umap/uploads
+
+volumes:
+  data:
+  db:
+```

mkdocs.yml

@@ -7,5 +7,6 @@ nav:
 - how-tos:
   - Ubuntu from scratch: ubuntu.md
   - Customize your uMap style: custom.md
+  - Install with Docker: docker.md
 - Changelog: changelog.md
 theme: readthedocs