patch 8.2.0843: filetype elm not detected

Problem:    Filetype elm not detected.
Solution:   Recognize *.elm files. (closes #6157)
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index c881fde..c47a6b8 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -151,6 +151,7 @@
     \ 'ecd': ['file.ecd'],
     \ 'edif': ['file.edf', 'file.edif', 'file.edo'],
     \ 'elinks': ['/etc/elinks.conf', '/.elinks/elinks.conf'],
+    \ 'elm': ['file.elm'],
     \ 'elmfilt': ['filter-rules'],
     \ 'erlang': ['file.erl', 'file.hrl', 'file.yaws'],
     \ 'eruby': ['file.erb', 'file.rhtml'],
diff --git a/src/version.c b/src/version.c
index 641b375..349ecbe 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    843,
+/**/
     842,
 /**/
     841,