docs: add table of contents (#52)

Author: mikesposito

README.md

@@ -4,6 +4,52 @@ My personal Neovim configuration files.
 
 ![screenshot](./.github/assets/screenshot.png)
 
+## Table of Contents
+
+- [Quickstart](#quickstart)
+  - [Prerequisites](#prerequisites)
+  - [Installation](#installation)
+- [Configuration](#configuration)
+  - [Preferences](#preferences)
+- [Plugins](#plugins)
+  - [AI / Code Assistance](#ai--code-assistance)
+  - [Completion](#completion)
+  - [LSP](#lsp)
+  - [Syntax & Treesitter](#syntax--treesitter)
+  - [Debugging](#debugging)
+  - [Diagnostics](#diagnostics)
+  - [Git](#git)
+  - [File Navigation](#file-navigation)
+  - [UI / Window Management](#ui--window-management)
+  - [Terminal](#terminal)
+  - [Tmux Integration](#tmux-integration)
+  - [Editing](#editing)
+  - [Formatting](#formatting)
+  - [Markdown](#markdown)
+  - [Highlighting](#highlighting)
+  - [Theme](#theme)
+  - [Utilities](#utilities)
+- [Language Servers (Mason)](#language-servers-mason)
+  - [Adding or Customizing LSP Servers](#adding-or-customizing-lsp-servers)
+- [Keymaps](#keymaps)
+  - [Navigation](#navigation)
+  - [Window splitting](#window-splitting)
+  - [Pane / Tmux navigation](#pane--tmux-navigation)
+  - [Code navigation](#code-navigation)
+  - [Code documentation](#code-documentation)
+  - [Code actions](#code-actions)
+  - [Debug & Diagnostics](#debug--diagnostics)
+  - [Troubles](#troubles)
+  - [Window management](#window-management)
+  - [Search](#search)
+  - [Formatting](#formatting-1)
+  - [Diff](#diff)
+  - [Git](#git-1)
+  - [GitHub](#github)
+  - [Tab management](#tab-management)
+  - [Completion](#completion-1)
+  - [Treesitter](#treesitter)
+
 ## Quickstart
 
 ### Prerequisites