patch 8.2.4683: verbose check with dict_find() to see if a key is present

Problem:    Verbose check with dict_find() to see if a key is present.
Solution:   Add dict_has_key(). (Yegappan Lakshmanan, closes #10074)
diff --git a/src/proto/dict.pro b/src/proto/dict.pro
index 7db011d..30a3055 100644
--- a/src/proto/dict.pro
+++ b/src/proto/dict.pro
@@ -27,6 +27,7 @@
 int dict_add_dict(dict_T *d, char *key, dict_T *dict);
 long dict_len(dict_T *d);
 dictitem_T *dict_find(dict_T *d, char_u *key, int len);
+int dict_has_key(dict_T *d, char *key);
 int dict_get_tv(dict_T *d, char_u *key, typval_T *rettv);
 char_u *dict_get_string(dict_T *d, char_u *key, int save);
 varnumber_T dict_get_number(dict_T *d, char_u *key);