docs on obtaining tree node labels

[nick-youngblut]

Prior to delving into lineages at https://yulab-smu.top/treedata-book/chapter2.html#accesor-tidytree, it would be helpful to first simply explain how to do the basics, such as:

• Get all tip labels (e.g., tree$tip.label). Must one first convert the treedata object to a phylo or tibble object?
• Get all node labels (no just tips)
• Get all internal node labels
• Get all edge lengths

[nick-youngblut]

More generally, it is great to have just extensive documentation in https://yulab-smu.top/treedata-book/index.html, but often the UI is only described with complex examples, and given that there really isn't much function-level docs in the ggtree and tidytree packages, users must try to decipher the basic functionality from the complex examples in the book.

Specific examples:

• https://yulab-smu.top/treedata-book/index.html
• https://yulab-smu.top/treedata-book/index.html
  • not clear from Timescaled layout how the data information is actually coded in the tree object
• https://yulab-smu.top/treedata-book/chapter5.html#taxa-connection
• https://yulab-smu.top/treedata-book/chapter7.html#facet_plot

It would be great to have more simplified examples/docs explaining more of the basic UI of the functions.