createMilestone method
Creates a new milestone on the specified repository.
API docs: https://developer.github.com/v3/issues/milestones/#create-a-milestone
Implementation
Future<Milestone> createMilestone(
RepositorySlug slug, CreateMilestone request) {
return github.postJSON('/repos/${slug.fullName}/milestones',
body: GitHubJson.encode(request), convert: Milestone.fromJson);
}