I would like, if possible, to add the option of supporting local `Jenkinsfile` inside the repository.

The use case is that we are using a `GitHub Organization` job that picks up some repositories and run a specific `Jenkinsfile` that we specify from this plugin. The problem comes when we want to have some customisation or temporarily test something on one repository (or even one branch).

For that reason, I thought that it might be a good idea to specify some type of hierarchy:

• If repository already has `Jenkinsfile` and override is enabled; it uses the local one instead of the remote one, otherwise
• Remote Jenkinsfile is used