Calltree.nvim -> LITEE.nvim

[ldelossa]

Calltree.nvim will be renamed to LITEE.nvim

LITEE is an acronym for "lightweight integrated text editing environment".

This feels a little better since this module started out with just a call hierarchy view but has been adding the missing VS code features into Neovim.

The goal of this plugin now changes to provide a "IDE-lite" experience. LITEE will integrate features from VSCode but in a way that (hopefully) feels lightweight and vim-native. LITEE should not feel like a full-blown IDE, but rather a set of added features.