Update documentation to address CRAN notes

[villegar]

CRAN notes

Version: 1.13-8
Check: CRAN incoming feasibility
Result: NOTE 
  Maintainer: ‘Matt Taddy <mataddy@gmail.com>’
  
  No Authors@R field in DESCRIPTION.
  Please add one, modifying
    Authors@R: person(given = "Matt",
                      family = "Taddy",
                      role = c("aut", "cre"),
                      email = "mataddy@gmail.com")
  as necessary.
  
  The Description field contains
    Paths for Concave Regularization', <arXiv:1308.5623>.
  Please refer to arXiv e-prints via their arXiv DOI <doi:10.48550/arXiv.YYMM.NNNNN>.
Flavors: [r-devel-linux-x86_64-debian-clang](https://www.r-project.org/nosvn/R.check/r-devel-linux-x86_64-debian-clang/gamlr-00check.html), [r-devel-linux-x86_64-debian-gcc](https://www.r-project.org/nosvn/R.check/r-devel-linux-x86_64-debian-gcc/gamlr-00check.html)

Version: 1.13-8
Check: Rd files
Result: NOTE 
  checkRd: (-1) naref.Rd:13: Lost braces
      13 | \details{ For every \code{factor} or \code{character} column in \code{x}, \code{naref} sets \code{NA} as the reference level for a \code{factor} variable. Columns coded as \code{character} class are first converted to factors via \R{factor(x)}.  If \code{impute=TRUE} then the numeric columns are converted to two columns, one appended \code{.x} that contains imputed values and another appended \code{.miss} which is a binary variable indicating whether the original value was missing.  Numeric columns are returned without change if \code{impute=FALSE} or if they do not contain any missing values.  
         |

Context

This task was proposed by R Core developer Kurt Hornik as part of an initiative to improve CRAN package documentation. Packages with public repositories (GitHub, GitLab, Bitbucket) and a higher number of reverse dependencies were prioritised. This PR has been completed as part of an R Dev Day at the University of Warwick on 12 Sept 2025 (see r-devel/r-dev-day#110).