Fix typo in README (instructions for running tests): Change 'npm rest' to 'npm test'

[kayush614]

Because

The current instructions in step 4 contain a typo (npm rest) which causes the command to fail if a user copies and pastes it directly. This fixes it to the correct npm test command.

This PR

• Fixes a typo in README.md step 4: changes npm rest helloWorld to npm test helloWorld.

Issue. #606

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. 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

[kayush614]

Apologies, I missed that this was just assigned to @thuang3316. Closing this now to respect the assignment workflow.