patch 9.1.0424: filetype: slint files are not recognized

Problem:  filetype: slint files are not recognized
Solution: Detect '*.slint' files as slint filetype,
          include basic sling filetype plugin
          (Riley Bruins)

closes: #14808

Signed-off-by: Riley Bruins <ribru17@hotmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/.github/MAINTAINERS b/.github/MAINTAINERS
index e5c88f4..d6fd02b 100644
--- a/.github/MAINTAINERS
+++ b/.github/MAINTAINERS
@@ -216,6 +216,7 @@
 runtime/ftplugin/sdoc.vim		@gpanders
 runtime/ftplugin/sed.vim		@dkearns
 runtime/ftplugin/sh.vim			@dkearns
+runtime/ftplugin/slint.vim		@ribru17
 runtime/ftplugin/solidity.vim		@cothi
 runtime/ftplugin/solution.vim		@dkearns
 runtime/ftplugin/spec.vim		@ignatenkobrain