patch 8.2.0360: yaml files are only recognized by the file extension

Problem:    Yaml files are only recognized by the file extension.
Solution:   Check for a line starting with "%YAML". (Jason Franklin)

runtime/scripts.vim

@@ -376,6 +376,10 @@ else
   elseif s:line1 =~? '-\*-.*erlang.*-\*-'
     set ft=erlang
 
+  " YAML
+  elseif s:line1 =~# '^%YAML'
+    set ft=yaml
+
   " CVS diff
   else
     let s:lnum = 1

src/testdir/test_filetype.vim

@@ -601,6 +601,7 @@ let s:script_checks = {
       \ 'haskell': [['#!/path/haskell']],
       \ 'cpp': [['// Standard iostream objects -*- C++ -*-'],
       \         ['// -*- C++ -*-']],
+      \ 'yaml': [['%YAML 1.2']],
       \ }
 
 func Test_script_detection()

src/version.c

@@ -738,6 +738,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    360,
 /**/
     359,
 /**/