Set up deployment of docker images

Using the branch update_compose, set up a GitHub Action to publish docker images to the GitHub container registry.

Create a new GitHub action that runs when code is pushed to main
Create new file .github/workflows/publish.yml, which only runs when code is pushed to main
```
on:
push:
branches:
  - main
```
- See example of publishing step here: https://docs.github.com/en/packages/managing-github-packages-using-github-actions-workflows/publishing-and-installing-a-package-with-github-actions#upgrading-a-workflow-that-accesses-a-registry-using-a-personal-access-token

We have two images to publish, using "client.Dockerfile" and "server.Dockerfile" (used with --file in the above example link). Also, for now make sure to specify the tag "development" instead of "latest".

GMOD / Apollo3

Set up deployment of docker images #366