Note: GitHub-hosted runners are not currently supported on GitHub Enterprise Server. You can see more information about planned future support on the GitHub public roadmap.
About YAML syntax for workflows
Workflow files use YAML syntax, and must have either a .yml or .yaml file extension. If you're new to YAML and want to learn more, see "Learn YAML in Y minutes."
You must store workflow files in the .github/workflows directory of your repository.