[FEATURE] Automatically use the default k3d-default.yaml file if present in current directory

[maacarbo]

Scope of your request

Allow automatic config file pickup at startup.

Describe the solution you'd like

It would be nice to have k3d picking up the default generated k3d config init (k3d-default.yaml) config file if present in the current directory, without having to specify --config when creating/deleting/managing a cluster.