patch 8.2.4721: cooklang files are not recognized

Problem:    Cooklang files are not recognized.
Solution:   recognize *.cook files. (Goc Dundar, closes #10120)
diff --git a/src/version.c b/src/version.c
index be3b669..1b2a188 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4721,
+/**/
     4720,
 /**/
     4719,