Javascript Course, More Testing Lesson: Adds Resources for Dependency Injection

[CCeph]

Because

Follow up to issue #26391. The "More Testing" lesson in the javascript course has a video that uses dependency injection frequently, but the students are never taught what dependency injection is. Hence, they can be overwhelmed or confused.

This PR

• Adds two resources for students to learn about dependency injection.

Issue

Closes #26391

Additional Information

N/A

Pull Request Requirements

• [x ] I have thoroughly read and understand The Odin Project Contributing Guide
• [x ] 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
• [ x] The Because section summarizes the reason for this PR
• [ x] The This PR section has a bullet point list describing the changes in this PR
• [ x] If this PR addresses an open issue, it is linked in the Issue section
• [ x] If any lesson files are included in this PR, they have been previewed with the Markdown preview tool to ensure it is formatted correctly
• [ x] If any lesson files are included in this PR, they follow the Layout Style Guide