Add Eloquent JavaScript to javascript/curated-links.md

[mergeworthy]

Eloquent JavaScript is a free online book that's widely recommended for beginners learning JavaScript well — it'd be a great addition to the JS resources list.

Where it should go

resources/javascript/curated-links.md, under the "Learning the language" section, in alphabetical order (it goes between the existing entries).

Suggested entry

- [Eloquent JavaScript](https://eloquentjavascript.net/) — A free online book that teaches JavaScript fundamentals through worked examples and exercises.

Acceptance criteria

• The entry is added to the "Learning the language" section of resources/javascript/curated-links.md.
• It's placed in correct alphabetical order within the section.
• The format matches existing entries exactly: - [Title](url) — one-line description.
• No other content is changed.

Estimated time

~10 minutes.

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