patch 8.2.2719: Vim9: appending to dict item doesn't work in a :def function

Problem:    Vim9: appending to dict item doesn't work in a :def function.
Solution:   Implement assignment with operator on indexed item.

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2719,
 /**/
     2718,
 /**/