[Feature] Add Table of Contents

## Problem
The current documentation page of the vocabulary design system lacks a well-structured table of contents to enable users to jump to sections they need directly without having to scroll through a large amount of content. As of now, there are only three links that provide basic navigation on the page.

## Description

- Create a table of contents that's accessible from the sidebar and allows users to jump into any section. The table of contents will break down each section into categories.
- Some sections will also be broken into subsections. For example, the components section will also have subsections and links to each component.

## Alternatives

- To continue with the current navigation, but this would result in users having to scroll through long sections to find the information they need.

- Use a simple top navigation bar instead of a sidebar, but it may limit the space for more detailed sections and make it less easier to locate specific content quickly.

## Implementation

- [x] I would be interested in implementing this feature.

No files or tests are named. Start by locating the documentation page and its existing sidebar or navigation entry points, then map the documented sections and component subsections. Done means the sidebar exposes accessible links to each required section and subsection and users can jump to them without scrolling through the full page.

Written by the indexing model from the issue text.