Add smart debugging function for GreenNodeBuilder

[K4rakara]

As it is, debugging issues with GreenNodeBuilder isn't easy. Sure, you can dbg! it, but it doesn't label what the SyntaxKinds are, rather, it just displays them with their raw value.

I think it would be great to add a function that helps with this. Ideally it would log something like this:

[email protected]
	[email protected]
		[email protected] "pub"
		[email protected] " "
		[email protected]
			[email protected] "type"
			[email protected] " "
			[email protected]
				[email protected] "Foo"
			[email protected] " "
			[email protected] "="

The last node (and/or token) would likely be highlighted in green to signify that it is the current node.

If this would be a welcome addition, I would be more than happy to implement it, but I wanted to ask first.