patch 9.0.1419: Lean files are not recognized

Problem:    Lean files are not recognized.
Solution:   Add a pattern for Lean files. (Amaan Qureshi, closes #12177)
diff --git a/runtime/filetype.vim b/runtime/filetype.vim
index d68c273..0fe303c 100644
--- a/runtime/filetype.vim
+++ b/runtime/filetype.vim
@@ -1112,6 +1112,9 @@
 " Ld loader
 au BufNewFile,BufRead *.ld			setf ld
 
+" Lean
+au BufNewFile,BufRead *.lean			setf lean
+
 " Ledger
 au BufRead,BufNewFile *.ldg,*.ledger,*.journal			setf ledger
 
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index 41cac26..6b1b47b 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -320,6 +320,7 @@
     \ 'latte': ['file.latte', 'file.lte'],
     \ 'ld': ['file.ld'],
     \ 'ldif': ['file.ldif'],
+    \ 'lean': ['file.lean'],
     \ 'ledger': ['file.ldg', 'file.ledger', 'file.journal'],
     \ 'less': ['file.less'],
     \ 'lex': ['file.lex', 'file.l', 'file.lxx', 'file.l++'],
diff --git a/src/version.c b/src/version.c
index 45be73e..379980a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1419,
+/**/
     1418,
 /**/
     1417,