React Router: Add additional resources talking about loaders

[nikitarevenco]

Because

It was decided that it would be appropriate to include an additional resources about Loaders for the React Router lesson.

This PR

• Adds additional resource relating to loaders. Since this isn't just a small topic, I've included three resources that I personally found helpful should the learner decide to research into them.

Issue

Related to #27585

Additional Information

Pull Request Requirements

• I have thoroughly read and understand The Odin Project Contributing Guide
• The title of this PR follows the location of change: brief description of change format, e.g. Intro to HTML and CSS lesson: Fix link text
• The Because section summarizes the reason for this PR
• The This PR section has a bullet point list describing the changes in this PR
• If this PR addresses an open issue, it is linked in the Issue section
• If any lesson files are included in this PR, they have been previewed with the Markdown preview tool to ensure it is formatted correctly
• If any lesson files are included in this PR, they follow the Layout Style Guide

[MaoShizhong]

@nikitarevenco Thanks for adding this resource.
Could you resolve the merge conflict with the additional resources section? Once that's resolved, the lint action should rerun and resolve all the other lint errors, as they'll update to what the curriculum currently has.