squat 0.3.0

New features

• Added S3 specialization of the stats::predict() function for prcomp_qts
  objects.
• Added function qts2aats() which allows to switch from quaternion to
  axis-angle representation of rotations.
• Added usual operations +, -, * and inverse_qts() for quaternion time
  series using the Eigen
  library.

Small improvements

• Make sure quaternion geodesic mean is not flipped.
• Fix issues in PCA:
  • avoid numerical overflows due to bad choice of k in gam();
  • improved documentation;
  • Use same number of basis functions in uni- and multivariate decompositions.
• Updated GHA scripts and README.
• Fix bug related to Rcpp following RcppCore/Rcpp#1287.