Automatically restore winfixwidth when leaving the buffer

Close #512

Author: lambdalisue

autoload/fern/internal/drawer/auto_winfixwidth.vim

@@ -6,9 +6,14 @@ function! fern#internal#drawer#auto_winfixwidth#init() abort
   augroup fern_internal_drawer_auto_winfixwidth_init
     autocmd! * <buffer>
     autocmd BufEnter <buffer> call s:set_winfixwidth()
+    autocmd BufWinLeave <buffer> call s:restore_winfixwidth()
   augroup END
 endfunction
 
 function! s:set_winfixwidth() abort
   let &l:winfixwidth = winnr('$') isnot# 1
 endfunction
+
+function! s:restore_winfixwidth() abort
+  let &l:winfixwidth = 0
+endfunction