[Feature Request] - Optionally skip rendering the root node

[rparrett]

Description

For my use case, I'm not finding it useful to be able to collapse the root node of a tree, and displaying the root node of the tree directly below the component title is a bit redundant.

There would be no reason for my users to collapse the root node, so I don't want to let them.

I'm not sure that I described that well, so here's what I'm trying to accomplish:

 ╭tree-viewer─────────────────────────────────╮
 │🦄 Cargo.toml                               │
 │   target ▶                                 │
 │   Cargo.lock                               │
 │   .gitignore                               │
 │   .git ▶                                   │
 │   src ▶                                    │
 │                                            │
 ╰────────────────────────────────────────────╯

Changes

Add an option that when used, skips the root node like shown above.

Implementation

I am not completely up to speed yet, but I'd like to do something along the lines of

• Add a hide_root_node method to TreeView
• Add hide_root_node field to TreeWidget
• Add a separate render_root_node function to TreeWidget that just iterates children if hide_root_node is true, or calls iter_nodes if not.

I've implemented the render_root_node part and things seem to work.

If the approach above sounds acceptable, I'd be happy to attempt a PR with the rest.