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/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index eeca7a1..fb14c2e 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -654,6 +654,7 @@
     slang: ['file.sl'],
     sage: ['file.sage'],
     slice: ['file.ice'],
+    slint: ['file.slint'],
     slpconf: ['/etc/slp.conf', 'any/etc/slp.conf'],
     slpreg: ['/etc/slp.reg', 'any/etc/slp.reg'],
     slpspi: ['/etc/slp.spi', 'any/etc/slp.spi'],
diff --git a/src/version.c b/src/version.c
index d6f028d..b10e501 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    424,
+/**/
     423,
 /**/
     422,