Refactor docker documentation

This MR refactors the documentation:

• remove unmaintained docker-compose.yml example files
• move nginx reverse proxy to separate file
• fix some typos in docker README
• fix become smith steps
• rename "rpc" nodes to "mirror" nodes

docs/user/mirror.md

+# How to deploy a permanent rpc node on ĞDev network
+
+## Publish a node
+
+### Duniter part
+
+See [docker documentation](../../docker/README.md) to install, configure, and start a node.
+
+### Reverse proxy part
+
+See [nginx reverse proxy](./nginx_reverse_proxy.md).
+
+To go further, read [How to become a (black)smith](./smith.md)
+
+## Upgrade your node with minimal interruption
+
+1. Modify docker image tag on your compose file
+2. Run `docker compose pull`, this will pull the new image.
+3. Run `docker compose up -d --remove-orphans`, this will recreate the container
+4. Verify that your node restarted well `docker compose logs duniter-rpc`
+5. Remove the old image `docker rmi duniter/duniter-v2s:OLD_TAG`