Fix readme and add the job posting map of US to the dashboard

[andyzhangstat]

Hello all, please take of look of my commit and approve!

[render[bot]]

Your Render PR Server URL is https://dsci-532-2024-21-job-postings-pr-34.onrender.com.

Follow its progress at https://dashboard.render.com/web/srv-co7j6v21hbls73ba4g6g.