vim-patch:8.1.0586: :digraph output is not easy to read

Problem:    :digraph output is not easy to read.
Solution:   Add highlighting for :digraphs. (Marcin Szamotulski, closes vim/vim#3572)
            Also add section headers for :digraphs!.
eae8ae1b2b

src/nvim/ex_cmds.lua

@@ -758,7 +758,7 @@ return {
   },
   {
     command='digraphs',
-    flags=bit.bor(EXTRA, TRLBAR, CMDWIN),
+    flags=bit.bor(BANG, EXTRA, TRLBAR, CMDWIN),
     addr_type=ADDR_LINES,
     func='ex_digraphs',
   },