return to previous window if zig fmt returns error

ends automatic window switch to quickfix when `zig fmt` errors

Author: atweiden

autoload/zig/fmt.vim

@@ -69,6 +69,7 @@ function! zig#fmt#Format() abort
 
   if err != 0
     echohl Error | echomsg "zig fmt returned error" | echohl None
+    wincmd p
     return
   endif