runtime(gomod): add gomod filetype plugin

closes: #15060

Signed-off-by: yu-yk <yukkuen.yu@linktivity.co.jp>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/.github/MAINTAINERS b/.github/MAINTAINERS
index 5ebe93a..1957499 100644
--- a/.github/MAINTAINERS
+++ b/.github/MAINTAINERS
@@ -152,6 +152,7 @@
 runtime/ftplugin/graphql.vim	@ribru17
 runtime/ftplugin/gyp.vim		@ObserverOfTime
 runtime/ftplugin/go.vim			@dbarnett
+runtime/ftplugin/gomod.vim		@yu-yk
 runtime/ftplugin/gprof.vim		@dpelle
 runtime/ftplugin/haml.vim		@tpope
 runtime/ftplugin/hare.vim		@selenebun