Add Docker docs

docs/docker.md

@@ -0,0 +1,26 @@
+# Docker
+
+We don't do anything non-standard with Docker.
+
+Configuration of the Docker container is defined in the docker-compose files, found in `conf/compose/SERVICE.docker-compose.yml`.
+
+Aside from version upgrades, you will not usually need to edit the compose files.
+
+## Updates
+
+Deploying service upgrades is relatively easy. To keep track with updates we recommend either following the projects repositories on Github, or using their RSS/Atom feeds. See the links below for project release links.
+
+An example of deploying Mastodon upgrades:
+
+1. Replace all occurences of the version string (eg: `v4.3.6`) with the newer version (eg: `v4.3.8`) in the file `conf/compose/mastodon.docker-compose.yml`
+2. Re-run `run.sh`
+
+
+# Links
+- Learn the Docker basics: https://docker-curriculum.com/
+# Service releases
+- Mastodon: https://github.com/mastodon/mastodon/releases
+- Element: https://github.com/element-hq/element-web/releases
+- Synapse: https://github.com/element-hq/synapse/releases
+- Peertube: https://github.com/Chocobozzz/PeerTube/releases
+