Maintenance update

• Updated dependencies to latest versions.
• Switched to using GitHub Actions for building linux/amd64 Docker images.

First release - Hello World!

Finally - months of work is done and we're ready for a first release of Butler Auth.

Let's repeat that: This is the first version.

There will be bugs.
There are things that for sure can be improved.
You can help!

File issues when you find strange things or add feature suggestions.
GitHub's new discussion forums are good - feel free to use them!

And don't forget:
The documentation site is available at https://butler-auth.ptarmiganlabs.com.