patch 9.1.0995: filetype: shaderslang files are not detected

Problem:  filetype: shaderslang files are not detected
Solution: detect '*.slang' files as shaderslang filetype,
          include a filetype and syntax script (mtvare6)

Reference:
https://shader-slang.com/

closes: #16387

Signed-off-by: mtvare6 <mtvare6@proton.me>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index 54f0385..8f2fb4f 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -697,6 +697,7 @@
          'user-dirs.defaults', 'user-dirs.dirs', 'makepkg.conf', '.makepkg.conf',
          'file.mdd', '.env', '.envrc', 'devscripts.conf', '.devscripts', 'file.lo',
          'file.la', 'file.lai'],
+    shaderslang: ['file.slang'],
     sieve: ['file.siv', 'file.sieve'],
     sil: ['file.sil'],
     simula: ['file.sim'],
diff --git a/src/version.c b/src/version.c
index 699ad36..95567b7 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    995,
+/**/
     994,
 /**/
     993,