vim syntax highlight for f2j

Highlight the f2j code in Vim editor.

Usage

1. Make sure Vim can idenfity the *.sf file type.

   find $VIMRUNTIME/filetype.vim

   add

   " f2j
   
   au BufNewFile,BufRead .*sf           setf f2j
   

   For more details, type :help filetype in vim.

2. Put f2j.vim to $VIMRUNTIME/syntax/