Add Visualization and Diagram Tools section; fix Libraries category misplacements

[BilgeGates]

What does this PR add or change?

While reviewing the list I noticed that several board UI components — chessground, react-chessboard, chessboard.js, and chessboard2 — were sitting inside the Libraries section alongside chess-logic libraries (move generators, PGN parsers, engine wrappers). These are rendering components, not logic libraries, and grouping them together makes the section harder to scan for developers who need one but not the other.

This PR addresses that by:

• Adding a new Visualization and Diagram Tools section, as permitted by the contributing guidelines when a clear rationale is provided.
• Moving the four board-rendering components from Libraries into the new section.
• Moving Chessvision.ai from Analysis Tools into the new section — its primary function is diagram OCR, not game analysis.
• Adding a handful of missing tools that fit naturally into the new section: a diagram editor, a FEN utility, and a client-side diagram generator (chess-vision), all of which are actively maintained.

The new section sits between Libraries and APIs and Data Sources in the table of contents, which keeps the developer-tooling categories grouped together logically.

Checklist

• I read contributing.md.
• The entry follows the required format: - [Name](link) - Description.
• The description starts with a capital letter and ends with a period.
• The resource is actively maintained (updated within the last 12 months).
• The resource is not already on the list.
• The entry is in the correct category.
• npx awesome-lint passes locally.

Link to the resource

https://github.com/bilgegates/chess-vision