JS Foundations Exercises: Group exercises by lessons

[zunaid-hassan]

Because

The JavaScript Foundations exercises are being grouped according to the lessons they were prescribed in.

This PR

1. Creates folders for the lessons
2. Moves the relevant exercise sub-folders into their relevant lesson folders
3. Resets the exercise folder numbering within each lesson folder
4. Updates exercise README files to reflect the new numbering
5. Updates the repo README with the new folder path example

Issue

Closes #665
Associated with TheOdinProject/curriculum#31366

Additional Information

N/A

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. 01_helloWorld: Update test cases
• 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 this PR includes any changes that affect the solution of an exercise, I've also updated the solution in the /solutions folder

[mao-sz]

Thanks. A couple more things need doing:

• While you've renumbered the exercise dirs' names, the READMEs for all the Loop and Arrays exercises and Object Basics exercises still contain the old numbers, so these also need renumbering.
• Step 4 of the repo README mentions a cd command with a path that'll need updating to the new one.

[zunaid-hassan]

Thanks, I have updated these.

[mao-sz]

🚀