patch 9.1.1957: filetype: bpftrace files are not recognized

Problem:  filetype: bpftrace files are not recognized
Solution: Detect *.bt files as btftrace filetype,
          include a btftrace filetype plugin (Stanislaw Gruszka)

closes: #18866

Signed-off-by: Stanislaw Gruszka <stf_xl@wp.pl>
Signed-off-by: Christian Brabandt <cb@256bit.org>

.github/MAINTAINERS

@@ -130,6 +130,7 @@ runtime/ftplugin/basic.vim				@dkearns
 runtime/ftplugin/brighterscript.vim			@ribru17
 runtime/ftplugin/brightscript.vim			@ribru17
 runtime/ftplugin/bst.vim				@tpope
+runtime/ftplugin/bpftrace.vim				@sgruszka
 runtime/ftplugin/c3.vim					@ttytm
 runtime/ftplugin/cabal.vim				@ribru17
 runtime/ftplugin/cedar.vim				@ribru17

runtime/autoload/dist/ft.vim

@@ -1736,6 +1736,8 @@ const ft_from_ext = {
   # BSDL
   "bsd": "bsdl",
   "bsdl": "bsdl",
+  # Bpftrace
+  "bt": "bpftrace",
   # C3
   "c3": "c3",
   "c3i": "c3",

runtime/ftplugin/bpftrace.vim

@@ -0,0 +1,14 @@
+" Vim filetype plugin
+" Language:     bpftrace
+" Maintainer:	Stanislaw Gruszka <stf_xl@wp.pl>
+" Last Change:	2025 Dec 05
+
+if exists('b:did_ftplugin')
+  finish
+endif
+let b:did_ftplugin = 1
+
+setlocal comments=sO:*\ -,mO:*\ \ ,exO:*/,s1:/*,mb:*,ex:*/,://
+setlocal commentstring=//\ %s
+
+let b:undo_ftplugin = "setlocal comments< commentstring<"

src/testdir/test_filetype.vim

@@ -148,6 +148,7 @@ def s:GetFilenameChecks(): dict<list<string>>
     blank: ['file.bl'],
     blueprint: ['file.blp'],
     bp: ['Android.bp'],
+    bpftrace: ['file.bt'],
     brighterscript: ['file.bs'],
     brightscript: ['file.brs'],
     bsdl: ['file.bsd', 'file.bsdl'],

src/version.c

@@ -729,6 +729,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1957,
 /**/
     1956,
 /**/