Improvements before first CRAN release

[nanxstats]

General improvements

• Set Yujie as maintainer.
• Replace all %>% with |> to avoid depending on magrittr.
• Add inst/WORDLIST and run spell check spelling::spell_check_package(), fix all typos.
• Update LICENSES_THIRD_PARTY with proper license links and format.
• Update copyright year and text format.

Style and documentation

• Format roxygen2 documentation following tidyverse style guide.
• Use @noRd for internal functions and remove them from _pkgdown.yml: n_subject(), avg_event(), avg_duration(), to_sentence().
• Run styler::style_pkg() to stylize code.
• Fix code linting issues using seq_along() and seq_len().

Vignettes

• Unify vignette YAML header format.
• Add a BibTeX file for proper citation management in rate-compare.Rmd.
• Remove descriptions from the vignette on reducing number of strong dependencies and add an issue Reduce the number of strong dependencies #107 instead.

[nanxstats]

Done.