BMT 0.1.3

Minor changes

• Corrected spelling errors in documentation files.
• Corrected the Version field in the DESCRIPTION file to follow the required X.Y.Z format.
• Added the Authors@R field to DESCRIPTION and removed deprecated Author and Maintainer fields.
• Set Encoding: UTF-8 in DESCRIPTION as required by roxygen2.
• Added missing @export tags to functions intended to be public.
• Suppressed export of internal S3 method startargdefault by omitting the @export tag.
• Reorganized roxygen blocks to avoid multiple @rdname tags in the same block.
• Fixed invalid URLs and replaced direct arXiv: references with proper DOIs.