Add rego support, closes #406

ftdetect/polyglot.vim

@@ -1103,6 +1103,17 @@ au BufNewFile,BufRead .merlin       set ft=merlin
   augroup end
 endif
 
+if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'rego') == -1
+  augroup filetypedetect
+  " rego, from rego.vim in tsandall/vim-rego
+autocmd BufRead,BufNewFile *.rego set filetype=rego
+
+" Use # as a comment prefix
+setlocal comments=b:#,fb:-
+setlocal commentstring=#\ %s
+  augroup end
+endif
+
 if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'ruby') == -1
   augroup filetypedetect
   " ruby, from ruby.vim in vim-ruby/vim-ruby