Add missing CHANGELOG entry for parseString

Change-Id: Ieb293ac02d97cf454231a27a82bf9dade567ada5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/106321
Auto-Submit: Paul Berry <paulberry@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
diff --git a/pkg/analyzer/CHANGELOG.md b/pkg/analyzer/CHANGELOG.md
index 37ac0ad..54c3fde 100644
--- a/pkg/analyzer/CHANGELOG.md
+++ b/pkg/analyzer/CHANGELOG.md
@@ -13,6 +13,11 @@
   impacts to value returned by `FunctionType.displayName` and
   `FunctionType.toString` and `ExecutableElement.toString`. Client code might be
   broken if it depends on the content of the returned value.
+* Introduced the function `parseString` to the public API.  This can be used in
+  place of the deprecated functions `parseCompilationUnit` and
+  `parseDirectives`.  Note that there is no option to parse only directives,
+  since this functionality is broken anyway (`parseDirectives`, despite its
+  name, parses the entire compilation unit).
 
 ## 0.36.3
 * Deprecated `AstFactory.compilationUnit`.  In a future analyzer release, this