patch 9.0.0448: SubRip files are not recognized

Problem:    SubRip files are not recognized.
Solution:   Add a pattern for SubRip. (closes #11113)

runtime/filetype.vim

@@ -1723,6 +1723,9 @@ au BufNewFile,BufRead *.sdl,*.pr		setf sdl
 " sed
 au BufNewFile,BufRead *.sed			setf sed
 
+" SubRip
+au BufNewFile,BufRead *.srt			setf srt
+
 " svelte
 au BufNewFile,BufRead *.svelte			setf svelte
 

src/testdir/test_filetype.vim

@@ -531,6 +531,7 @@ let s:filename_checks = {
     \ 'squid': ['squid.conf'],
     \ 'squirrel': ['file.nut'],
     \ 'srec': ['file.s19', 'file.s28', 'file.s37', 'file.mot', 'file.srec'],
+    \ 'srt': ['file.srt'],
     \ 'sshconfig': ['ssh_config', '/.ssh/config', '/etc/ssh/ssh_config.d/file.conf', 'any/etc/ssh/ssh_config.d/file.conf', 'any/.ssh/config', 'any/.ssh/file.conf'],
     \ 'sshdconfig': ['sshd_config', '/etc/ssh/sshd_config.d/file.conf', 'any/etc/ssh/sshd_config.d/file.conf'],
     \ 'st': ['file.st'],

src/version.c

@@ -703,6 +703,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    448,
 /**/
     447,
 /**/