Create docker image for github self hosted windows runner

[MohamedAlmaki]

Docker image for self-hosted GitHub Windows runner for the mantidproject/mantid repository.

The Docker image is based on the same Jenkins node image but removes Jenkins dependencies and installs GitHub Runner dependencies. This ensures consistency as we transition from Jenkins to GitHub Actions. For more details, see the README.

The image has been uploaded as version 0.1 to our container repository here.

You can see the runner in action in this PR.

Closes #158

[thomashampson]

Small addition is required to documentation to ensure the docker container is given a name.
Otherwise it is looking good to me. I was able to create a docker container following the instructions and it is runner here:
thomashampson/mantid_github_actions_test#6
I am also attempting to run the system tests on Windows using this docker image because I think we should test that before merging this PR. We will need to run system tests in the nightly builds, so we might as well check that they work now:
thomashampson/mantid_github_actions_test#7

[thomashampson]

system tests all run and pass on Windows when using this docker image:
thomashampson/mantid_github_actions_test#7

[thomashampson]

I've tested the docker image myself in a fork, and confirmed that system tests also run and pass with this image.