docs: add "tidyverse" to WORDLIST

Spellcheck on PR #223 flagged "tidyverse" in NEWS.md as misspelled
because the word wasn't yet in inst/WORDLIST.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: d-morrison

inst/WORDLIST

@@ -61,6 +61,7 @@ strat
 stratifications
 tbl
 testthat
+tidyverse
 toolchain
 unstratified
 vh