Issue #6236: Add github-handle to Layne Mostyn in ballot-nav

[jonnyoe]

Fixes #6236

What changes did you make?

• Added the new gh-handle variable under Layne Mostyn in ballot-nav.md

Why did you make the changes (we will use this info to test)?

• Creates a single variable github-handle to hold the github handle for each member of the leadership team. Reduces redundancy by progressively replacing the github and picture variables in the project file.

Screenshots of Proposed Changes Of The Website (if any, please do not screen shot code changes)

• No Visual changes (Confirmed via docker)

[github-actions]

Want to review this pull request? Take a look at this documentation for a step by step guide!

From your project repository, check out a new branch and test the changes.

git checkout -b jono4727-new-var-gh-handle-6236 gh-pages
git pull https://github.com/jono4727/website.git new-var-gh-handle-6236

---

Note that CONTRIBUTING.md cannot previewed locally; rather it should be previewed at this URL:

https://github.com/jono4727/website/blob/new-var-gh-handle-6236/CONTRIBUTING.md  

[JackCasica]

Hi ~ I'll be reviewing this PR today ~
Availability: (03/28)
ETA: EOD (03/28)

[JackCasica]

Hi Evan,

Thank you for the work you've put into this pull request! Here's what's great and what could be improved:

✅ What's Great:

You successfully added the new github-handle variable for Layne Mostyn, which was the main goal of this issue. Nice work!

🔍 Areas for Improvement:

The commit history in this PR includes 5 commits, but only one seems directly related to the issue at hand (#6536). The other 4 commits appear to be changes from earlier dates that have already been merged. In an effort to make the commit history as clear as possible, it may be best to create a new PR that includes just the most recent commit (sha 43a88d8).

Feel free to let me know if you have any questions or if you want to work through it on a video call together.

[jonnyoe]

Closing this PR to create a clean one.