Add documentation for Docker usage

Author: asbjornu

docs/input/docs/usage/docker.md

@@ -0,0 +1,27 @@
+---
+Order: 50
+Title: Docker
+Description: |
+    Use GitVersion through one of its many published Docker containers.
+---
+
+GitVersion can be used through one of its many published Docker
+containers. The list of available containers can be found on
+[Docker Hub][docker-hub]. Once you've found the image you want to use,
+you can run it like this:
+
+```shell
+docker run --rm --volume "$(pwd):/repo" gittools/gitversion:6.0.0-fedora.36-6.0 /repo
+```
+
+The above command will run GitVersion with the current directory
+mapped to `/repo` inside the container (the `--volume "$(pwd):/repo"`
+part). The `/repo` directory is then passed in as the argument
+GitVersion should use to calculate the version.
+
+The `--rm` flag will remove the container after it has finished
+running.
+
+[Explore GitVersion on Docker Hub][docker-hub]{.btn .btn-primary}
+
+[docker-hub]: https://hub.docker.com/r/gittools/gitversion