feature: add jQuery courses in free-courses-en.md

[RUIZEN9]

What does this PR do?

Add resources

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For resources

Description

Adding two free video course playlists on jQuery. These tutorials cover the fundamentals of using the JavaScript library for DOM manipulation and AJAX calls.

1. jQuery - Beau teaches JavaScript
2. jQuery Tutorials

Why is this valuable (or not)?

While newer frameworks exist, jQuery remains prevalent in legacy codebases and for specific DOM manipulation tasks. These free playlists are valuable for developers needing to learn, maintain, or update projects that rely on jQuery.

How do we know it's really free?

Both resources are freely available as video playlists on YouTube.

For book lists, is it a book? For course lists, is it a course? etc.

These are free online video course/tutorial playlists.

Checklist:

• Search for duplicates.
• Include author(s) and platform where appropriate.
• Put lists in alphabetical order, correct spacing.
• Add needed indications (PDF, access notes, under construction).
• Used an informative name for this pull request.

Follow-up

• Check the status of GitHub Actions and resolve any reported warnings!