GIthub workflows resource

[g4s8]

Investigate how to design workflow resources and implement it.
Parent #46

[orlovm]

@g4s8 Github does not provide public API methods to create/edit workflows.
According to API documentation, available methods are: list workflows, get workflow, enable/disable workflow, create dispatch event, get workflow usage info.
Therefore implementing workflows manage commands does not seem very useful.

[g4s8]

@orlovm ok, let me check this issue. I think we can configure workflows by applying user's templates to generate workflow-configuration files and upload it via API (similar to readme spec)