✨ Implement extension methods to transform node collections

[pleonex]

Implement the three overloads of TransformWith to IEnumerable<Node> and NavigableNodeCollection<Node>, so that we can transform all the nodes in one line.

This PR closes #194

Quality check list

• Related code has been tested automatically or manually
• Related documentation is updated
• I acknowledge I have read and filled this checklist and accept the
  developer certificate of origin

Acceptance criteria

• We can transform children with the same converter in one line

Follow-up work

None

Example

using Node overlays = NodeFactory.FromDirectory("overlays");
overlays.Children.TransformCollectionWith<BlzDecompressor>();