Add CHANGELOG entry for lexer prepro EOF fix (#527)

Author: youdie006

CHANGELOG.md

@@ -14,6 +14,9 @@ see [CONTRIBUTING.md](CONTRIBUTING.md#release-instructions-for-a-new-version) fo
    "permission denied" error
  - fix: tablex.mapn could take a long time if no args provided
    [#521](https://github.com/lunarmodules/Penlight/pull/521)
+ - fix(lexer): a preprocessor directive on the final line with no trailing
+   newline is now recognized as a single `prepro` token
+   [#527](https://github.com/lunarmodules/Penlight/pull/527)
 
 ## 1.15.0 (2026-Jan-4)
  - docs: many (small) documentation updates and fixes