patch 9.1.0779: filetype: neomuttlog files are not recognized

Problem:  filetype: neomuttlog files are not recognized
Solution: detect '*.neomuttdebug' file as neomuttlog filetype,
          include neomuttlog syntax script (Richard Russon)

closes: #15858

Co-authored-by: AvidSeeker <avidseeker7@protonmail.com>
Signed-off-by: Richard Russon <rich@flatcap.org>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index 29bb7b5..1c66042 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -2538,6 +2538,12 @@
 	:let msql_minlines = 200
 
 
+NEOMUTT			*neomutt.vim* *ft-neomuttrc-syntax* *ft-neomuttlog-syntax*
+
+To disable the default NeoMutt log colors >
+
+	:let g:neolog_disable_default_colors = 1
+
 N1QL						*n1ql.vim* *ft-n1ql-syntax*
 
 N1QL is a SQL-like declarative language for manipulating JSON documents in