add_github_actions_pkgdown_badge: Add a Website badge
Description
This function adds a Website badge to the README.Rmd. This function
must be run after add_github_actions_pkgdown() which will setup
GitHub Actions to build and deploy the package website.
Make sure that 1) a README.Rmd file exists at the project root and 2) it
contains a block starting with the line <!-- badges: start --> and ending
with the line <!-- badges: end -->.