add a link to the data driven file format docs (#79412)

packages/flutter/lib/fix_data.yaml

@@ -2,13 +2,16 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-# For details regarding *Flutter Fix* feature, see
+# For details regarding the *Flutter Fix* feature, see
 # https://flutter.dev/docs/development/tools/flutter-fix
 
 # Please add new fixes to the top of the file, separated by one blank line
 # from other fixes. In a comment, include a link to the PR where the change
 # requiring the fix was made.
 
+# For documentation about this file format, see
+# https://dart.dev/go/data-driven-fixes.
+
 version: 1
 transforms: