Add changelog

Author: thomasqueirozb

changelog.d/1553.missing-functions.fix.md

@@ -0,0 +1,4 @@
+Fixed an issue where `split_path`, `basename`, `dirname` had not been added to VRL's standard
+library and, therefore, appeared to be missing and were inaccessible in the `0.28` release.
+
+authors: thomasqueirozb