Feat/Add @workflow.register_node decorator

[Howe829]

Adding graph.register_node decorator for easily register a node to the workflow.

[hinthornw]

oh it's kinda convenient. Will defer to @nfcampos on the approval though

[nfcampos]

I'm not opposed to this as long as we can do it inside the existing add_node method

[Howe829]

Hi there, I've tried to make it inside the add_node method.PLTAL It may looks a little bit tricky but this is the best way for me to make add_node as a decorator as well as thinking about the forward compatibility.

[Glinte]

Any updates on this? Seems quite helpful