textclasstutorial 0.1.0

• Converted the original code repository into an installable R package.
• Added documented HTML, preprocessing, DTM, TF-IDF, similarity, evaluation, fold-generation, and Naive Bayes functions.
• Added two end-to-end tutorials and a comprehensive testthat suite.
• Preserved the ten original code listings under inst/legacy-code/.
• Added cross-platform R CMD check automation.