docs: add SQLite3 $foreignKeys to changelog

Author: kenjis

user_guide_src/source/changelogs/v4.2.0.rst

@@ -93,6 +93,7 @@ Database
     - Added the class ``CodeIgniter\Database\RawSql`` which expresses raw SQL strings.
     - :ref:`select() <query-builder-select-rawsql>`, :ref:`where() <query-builder-where-rawsql>`, :ref:`like() <query-builder-like-rawsql>`, :ref:`join() <query-builder-join-rawsql>` accept the ``CodeIgniter\Database\RawSql`` instance.
     - ``DBForge::addField()`` default value raw SQL string support. See :ref:`forge-addfield-default-value-rawsql`.
+- SQLite3 has a new Config property ``$foreignKeys`` that enables foreign key constraints.
 
 Helpers and Functions
 =====================