Handle LSP codes for %code% in message formats

fixes #1767

test/test_ignoring_linters.vader

@@ -190,6 +190,7 @@ Execute(Buffer ignore lists should be applied for tsserver):
   \     'lnum': 2,
   \     'col': 14,
   \     'nr': 1005,
+  \     'code': '1005',
   \     'type': 'E',
   \     'end_col': 15,
   \     'end_lnum': 2,