patch 8.2.4932: not easy to filter the output of maplist()

Problem:    Not easy to filter the output of maplist().
Solution:   Add mode_bits to the dictionary. (Ernie Rael, closes #10356)
diff --git a/src/map.c b/src/map.c
index 48196f2..a93cb2e 100644
--- a/src/map.c
+++ b/src/map.c
@@ -2303,6 +2303,7 @@
     dict_add_number(dict, "nowait", mp->m_nowait ? 1L : 0L);
     dict_add_string(dict, "mode", mapmode);
     dict_add_number(dict, "abbr", abbr ? 1L : 0L);
+    dict_add_number(dict, "mode_bits", mp->m_mode);
 
     vim_free(mapmode);
 }