Clarify the nature of the Docker alternative and add links

Importantly this pushes this option to being secondary and
clarifies which of the build steps it replaces.

Note that this also removes the instructions on how to use Docker.
If users are not already familiar with Docker & Docker Compose
then they are equally not equipped to judge the security posture
that it presents.

Author: PeterJCLaw

README.md

@@ -4,12 +4,6 @@ The Student Robotics public documentation.
 
 ## Getting Started
 
-For ease of setup, a Docker container is provided. Simply install Docker and `docker-compose`, and run `docker-compose up`.
-
-Once setup, the site will be accessible on http://localhost:4000/docs/
-
-### Manual
-
 0. [Clone this repo][clone-repo]
 
 1. [Install Ruby][install-ruby]
@@ -28,6 +22,14 @@ Once setup, the site will be accessible on http://localhost:4000/docs/
 
 4. View the website at <http://localhost:4000/docs/>
 
+### Docker
+
+If you would prefer to [install Docker][install-docker] and [Docker Compose][install-docker-compose]
+rather than Ruby directly, these can be used instead.
+
+Note that this approach exposes the development server to the network you're
+using, which may present a security risk.
+
 ## Making changes
 
 When you've made a change, either push it to a forked repository, or to a
@@ -58,6 +60,8 @@ page titles.
 
 [clone-repo]: https://docs.github.com/en/repositories/creating-and-managing-repositories/cloning-a-repository
 [install-ruby]: https://www.ruby-lang.org/en/documentation/installation/
+[install-docker]: https://docs.docker.com/engine/install/
+[install-docker-compose]: https://docs.docker.com/compose/install/
 [raise-a-pr]: https://github.com/srobo/docs/pull/new/master
 [cspell]: https://cspell.org/
 [vscode-cspell]: https://marketplace.visualstudio.com/items?itemName=streetsidesoftware.code-spell-checker