JavaScript Library: mention Git repo set up requirement

[SeanAverS]

Because

Mention requirement of Git repo in set up instructions so reader has the necessary components for the project

This PR

• In the first point of the Assignment section mention that a Git repo needs to be set up

Issue

Closes #28820

Additional Information

Pull Request Requirements

• I have thoroughly read and understand The Odin Project curriculum 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]

Closing for the same reason as #28833. You're welcome to comment on an issue requesting assignment but please do not open a PR for it unless assigned.

[SeanAverS]

Apologies @MaoShizhong thank you the clarification