Add the updateUserName function

[BrendanTurner1]

Description

This adds the function to display the user name in the DOM

Contributors

@BrendanTurner1

Screenshot(s)

Notes

innerHTML subject to changes or additional features.

Checklist

• [x] My PR has an appropriately descriptive and concise title.
• [x] My PR denotes any/all team members who contributed to it.
• [x] My code follows the Turing Style Guides and best practices.
• [x] I ran the code locally and verified that there are no visible errors.
• [x] feat: My PR clearly describes what feature I'm adding and any changes needed to make it work. (if applicable)