patch 9.0.0448: SubRip files are not recognized

Problem:    SubRip files are not recognized.
Solution:   Add a pattern for SubRip. (closes #11113)
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index b8fccb2..62867e3 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -531,6 +531,7 @@
     \ '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'],
diff --git a/src/version.c b/src/version.c
index da11368..2764ad9 100644
--- a/src/version.c
+++ b/src/version.c
@@ -704,6 +704,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    448,
+/**/
     447,
 /**/
     446,