datetime: changelog for datetime module

Introduced new date/time/interval types support to lua and storage engines.

Closes tarantool#5941
Closes tarantool#5946

Author: tsafin

changelogs/unreleased/gh-5941-datetime-type-support.md

@@ -0,0 +1,4 @@
+## feature/lua/datetime
+
+ * Introduce new builtin module for date/time/interval support - `datetime.lua`.
+   Support of new datetime type in storage engines (gh-5941, gh-5946).