GitHub.DistributedTask.ObjectTemplating.TemplateValidationException: The template is not valid. /home/runner/work/mithril.js/mithril.js/./.github/actions/setup/action.yml (Line: 27, Col: 7): Required property is missing: shell
at GitHub.DistributedTask.ObjectTemplating.TemplateValidationErrors.Check()
at GitHub.Runner.Worker.ActionManifestManager.ConvertRuns(IExecutionContext executionContext, TemplateContext templateContext, TemplateToken inputsToken, String fileRelativePath, MappingToken outputs)
at GitHub.Runner.Worker.ActionManifestManager.Load(IExecutionContext executionContext, String manifestFile)