Move the dashboard onto GitHub Actions

[coatless]

Hi,

I noticed earlier today that the repo's URL (https://tidyverse.org/dashboard) was receiving a 404 from https://colorado.posit.co/rsc/tidyverse-dashboard/.

This PR address the 404 by moving it away from Colorado and onto GitHub through GitHub Actions with a GitHub Pages deploy.

[!NOTE]

Due to the size of the dashboard, a personal GITHUB PAT token is required to avoid running into a stream issue.