patch 9.0.1430: Livebook files are not recognized

Problem:    Livebook files are not recognized.
Solution:   Add a pattern for Livebook files. (Mathias Jean Johansen,
            closes #12203)

runtime/filetype.vim

@@ -1162,6 +1162,9 @@ au BufNewFile,BufRead *.lite,*.lt		setf lite
 " LiteStep RC files
 au BufNewFile,BufRead */LiteStep/*/*.rc		setf litestep
 
+" Livebook
+au BufNewFile,BufRead *.livemd			setf livebook
+
 " Login access
 au BufNewFile,BufRead */etc/login.access	setf loginaccess
 

src/testdir/test_filetype.vim

@@ -336,6 +336,7 @@ let s:filename_checks = {
     \ 'lite': ['file.lite', 'file.lt'],
     \ 'litestep': ['/LiteStep/any/file.rc', 'any/LiteStep/any/file.rc'],
     \ 'logcheck': ['/etc/logcheck/file.d-some/file', '/etc/logcheck/file.d/file', 'any/etc/logcheck/file.d-some/file', 'any/etc/logcheck/file.d/file'],
+    \ 'livebook': ['file.livemd'],
     \ 'loginaccess': ['/etc/login.access', 'any/etc/login.access'],
     \ 'logindefs': ['/etc/login.defs', 'any/etc/login.defs'],
     \ 'logtalk': ['file.lgt'],

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1430,
 /**/
     1429,
 /**/