patch 8.2.2336: Vim9: not possible to extend dictionary with different type

Problem:    Vim9: it is not possible to extend a dictionary with different
            item types.
Solution:   Add extendnew(). (closes #7666)
diff --git a/runtime/doc/usr_41.txt b/runtime/doc/usr_41.txt
index 7d4e3a2..624bb93 100644
--- a/runtime/doc/usr_41.txt
+++ b/runtime/doc/usr_41.txt
@@ -640,6 +640,7 @@
 	insert()		insert an item somewhere in a List
 	add()			append an item to a List
 	extend()		append a List to a List
+	extendnew()		make a new List and append items
 	remove()		remove one or more items from a List
 	copy()			make a shallow copy of a List
 	deepcopy()		make a full copy of a List
@@ -669,6 +670,7 @@
 	empty()			check if Dictionary is empty
 	remove()		remove an entry from a Dictionary
 	extend()		add entries from one Dictionary to another
+	extendnew()		make a new Dictionary and append items
 	filter()		remove selected entries from a Dictionary
 	map()			change each Dictionary entry
 	mapnew()		make a new Dictionary with changed items