[Structure] Add trees

[geekygirlsarah]

Description

This issue is for adding a new structure for all languages that will let you compare a new aspect of a language. Ideally someone with many programming languages will help work on this.

This structure should be how to create and use various tree structures. This could include:

• What built-in libraries to include to add functionality (if needed or available)
• How to create basic tree objects
• What type of tree structure is created behind the scenes
• Does the tree self-balance
• How to add nodes (leaves) to the tree
• How to traverse the tree
• How to remove nodes
• How to create various types of other trees (binary, ternary. n-ary, AVL, red-black, b-tree etc.)

Or other things. It should take some thought on all of the features that any programming language could have. Upon making this PR, expect it to have some revisions as people from various programming language backgrounds offer suggestions.

Requirements

1. Look over the documentation at https://docs.codethesaur.us/thesaurus/add-new-structure/
2. Add a new file under web/thesauruses/_meta named whatever feels appropriate
3. Open up web/thesauruses/meta_info.json and add your new file to that file in the structures section.
4. Add in some categories, then add in the concepts under that
5. Feel free to use any _meta file as examples for how to do it
6. Make a PR and we can help test and review it