patch 8.2.3818: cannot filter or map characters in a string

Problem:    Cannot filter or map characters in a string.
Solution:   Make filter() and map() work on a string. (Naruhiko Nishino,
            closes #9327)
diff --git a/src/version.c b/src/version.c
index e9836ef..d48206f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -750,6 +750,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3818,
+/**/
     3817,
 /**/
     3816,