add support for Azure Devops Pipelines

[krancour]

Azure DevOps Pipelines doesn't have the slick support for reusable Docker-based tasks in the way that GitHub Actions or Bitbucket Pipelines does, but it would be possible to define a reusable template in a public repository and that template can include the steps to execute Bookkeeper within a Docker container based on the official image.

https://learn.microsoft.com/en-us/azure/devops/pipelines/process/templates?view=azure-devops#use-other-repositories