patch 9.0.0935: when using dash it may not be recognize as filetype "sh"

Problem:    When using dash it may not be recognize as filetype "sh".
Solution:   Add checks for "dash". (Eisuke Kawashima,closes #11600)
diff --git a/runtime/autoload/dist/script.vim b/runtime/autoload/dist/script.vim
index 9e41969..8c5441c 100644
--- a/runtime/autoload/dist/script.vim
+++ b/runtime/autoload/dist/script.vim
@@ -53,8 +53,8 @@
     name = 'wish'
   endif
 
-  # Bourne-like shell scripts: bash bash2 ksh ksh93 sh
-  if name =~ '^\(bash\d*\|\|ksh\d*\|sh\)\>'
+    # Bourne-like shell scripts: bash bash2 dash ksh ksh93 sh
+  if name =~ '^\(bash\d*\|dash\|ksh\d*\|sh\)\>'
     call dist#ft#SetFileTypeSH(line1)
 
     # csh scripts