feat: Add support for GitHub Environments

## Prerequisites:

* Is the functionality available in the GitHub UI? If so, please provide a link to information about the feature.
* Yes, available under Repository Settings -> Environment
* https://docs.github.com/en/actions/deployment/targeting-different-environments/using-environments-for-deployment

* Is the functionality available through the GitHub API? If the functionality is available, please provide links to the API documentation (https://developer.github.com/v3/) as well as the Octokit documentation (https://octokit.github.io/).
* https://docs.github.com/en/rest/deployments/environments

## New Feature

Same as https://github.com/repository-settings/app/issues/607
Manage GitHub Environments with safe-settings at `settings.yml` and `{repo}.yml`
From #381: Similar to branch protection rules it would be great to configure deployment protection rules, deployment branches, secrets, and variables