rrum 0.2.2 - Maintenance Release

Changes

• Added explicit dependencies on R (>= 4.3.0), Rcpp (>= 1.1.0), and
  RcppArmadillo (>= 15.0.2-2)
• Switched README.Rmd to README.qmd to use Quarto for rendering.
• Addressed deprecation warning of "replace conv_to<...>::from(X) with as_scalar(X)"
  by using arma::as_scalar(...) instead of conv_to<double>::from(...).
• Updated GitHub Action workflows.