Expand What's New and blurb

Author: StanFromIreland

Doc/whatsnew/3.15.rst

@@ -769,7 +769,8 @@ unicodedata
 * The Unicode database has been updated to Unicode 17.0.0.
 
 * Add :func:`unicodedata.isxidstart` and :func:`unicodedata.isxidcontinue`
-  functions.
+  functions to check whether a character can start or continue a
+  `Unicode Standard Annex #31 <https://www.unicode.org/reports/tr31/>`_ identifier.
   (Contributed by Stan Ulbrych in :gh:`129117`.)
 
 

Misc/NEWS.d/next/Library/2025-10-17-20-42-38.gh-issue-129117.X9jr4p.rst

@@ -1,2 +1,3 @@
 :mod:`unicodedata`: Add :func:`~unicodedata.isxidstart` and
-:func:`~unicodedata.isxidcontinue` functions.
+:func:`~unicodedata.isxidcontinue` functions to check whether a character can
+start or continue a `Unicode Standard Annex #31 <https://www.unicode.org/reports/tr31/>`_ identifier.