patch 9.0.2098: No filetype support for xcompose files

Problem:  No filetype support for xcompose files
Solution: Add filetype detection

closes: #13508

Signed-off-by: ObserverOfTime <chronobserver@disroot.org>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/.github/CODEOWNERS b/.github/CODEOWNERS
index cd64800..d99c8c7 100644
--- a/.github/CODEOWNERS
+++ b/.github/CODEOWNERS
@@ -237,6 +237,7 @@
 runtime/ftplugin/wast.vim		@rhysd
 runtime/ftplugin/wget.vim		@dkearns
 runtime/ftplugin/wget2.vim		@dkearns
+runtime/ftplugin/xcompose.vim		@ObserverOfTime
 runtime/ftplugin/xml.vim		@chrisbra
 runtime/ftplugin/xs.vim			@petdance
 runtime/ftplugin/zsh.vim		@chrisbra
@@ -525,6 +526,7 @@
 runtime/syntax/wget.vim			@dkearns
 runtime/syntax/wget2.vim		@dkearns
 runtime/syntax/xbl.vim			@dkearns
+runtime/syntax/xcompose.vim		@ObserverOfTime
 runtime/syntax/xmath.vim		@cecamp
 runtime/syntax/xml.vim			@chrisbra
 runtime/syntax/xs.vim			@petdance
diff --git a/runtime/filetype.vim b/runtime/filetype.vim
index 7fb92a2..df7624d 100644
--- a/runtime/filetype.vim
+++ b/runtime/filetype.vim
@@ -2537,6 +2537,9 @@
 " XS Perl extension interface language
 au BufNewFile,BufRead *.xs			setf xs
 
+" X compose file
+au BufNewFile,BufRead .XCompose,Compose	setf xcompose
+
 " X resources file
 au BufNewFile,BufRead .Xdefaults,.Xpdefaults,.Xresources,xdm-config,*.ad setf xdefaults
 
diff --git a/runtime/ftplugin/xcompose.vim b/runtime/ftplugin/xcompose.vim
new file mode 100644
index 0000000..7345c27
--- /dev/null
+++ b/runtime/ftplugin/xcompose.vim
@@ -0,0 +1,13 @@
+" Vim filetype plugin file
+" Language:	XCompose
+" Maintainer:	ObserverOfTime <chronobserver@disroot.org
+" Last Change:	2023 Nov 09
+
+if exists('b:did_ftplugin')
+  finish
+endif
+let b:did_ftplugin = 1
+
+setl comments=:# commentstring=#\ %s
+
+let b:undo_ftplugin = 'setl com< cms<'
diff --git a/runtime/syntax/xcompose.vim b/runtime/syntax/xcompose.vim
new file mode 100644
index 0000000..3637b9f
--- /dev/null
+++ b/runtime/syntax/xcompose.vim
@@ -0,0 +1,37 @@
+" Vim syntax file
+" Language:	XCompose
+" Maintainer:	ObserverOfTime <chronobserver@disroot.org>
+" Filenames:	.XCompose, Compose
+" Last Change:	2023 Nov 09
+
+" Comments
+syn keyword xcomposeTodo contained TODO FIXME XXX
+syn match xcomposeComment /#.*/ contains=xcomposeTodo
+
+" Includes
+syn keyword xcomposeInclude include nextgroup=xcomposeFile skipwhite
+syn match xcomposeFile /"\([^"]\|\\"\)\+"/ contained
+syn match xcomposeSubstitution /%[HLS]/ contained containedin=xcomposeFile
+
+" Modifiers
+syn keyword xcomposeModifier Ctrl Lock Caps Shift Alt Meta None
+syn match xcomposeModifierPrefix /\s*\zs[!~]\ze\s*/
+
+" Keysyms
+syn match xcomposeKeysym /<[A-Za-z0-9_]\+>/
+syn match xcomposeKeysym /[A-Za-z0-9_]\+/ contained
+syn match xcomposeString /"\([^"]\|\\"\)\+"/ contained nextgroup=xcomposeKeysym skipwhite
+syn match xcomposeColon /:/ nextgroup=xcomposeKeysym,xcomposeString skipwhite
+
+hi def link xcomposeColon Delimiter
+hi def link xcomposeComment Comment
+hi def link xcomposeFile String
+hi def link xcomposeInclude Include
+hi def link xcomposeKeysym Constant
+hi def link xcomposeModifier Function
+hi def link xcomposeModifierPrefix Operator
+hi def link xcomposeString String
+hi def link xcomposeSubstitution Special
+hi def link xcomposeTodo Todo
+
+let b:current_syntax = 'xcompose'
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index 6cfd69f..9a0a6da 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -799,6 +799,7 @@
     wsh: ['file.wsf', 'file.wsc'],
     wsml: ['file.wsml'],
     wvdial: ['wvdial.conf', '.wvdialrc'],
+    xcompose: ['.XCompose', 'Compose'],
     xdefaults: ['.Xdefaults', '.Xpdefaults', '.Xresources', 'xdm-config', 'file.ad', '/Xresources/file', '/app-defaults/file', 'Xresources', 'Xresources-file', 'any/Xresources/file', 'any/app-defaults/file'],
     xf86conf: ['xorg.conf', 'xorg.conf-4'],
     xhtml: ['file.xhtml', 'file.xht'],
diff --git a/src/version.c b/src/version.c
index 0883cae..a4cc261 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2098,
+/**/
     2097,
 /**/
     2096,