[vim] NERDTree hidden files enabled by default

vim/vimrc

@@ -70,6 +70,7 @@ nnoremap <leader>n :NERDTreeFocus<CR>
 nnoremap <C-n> :NERDTree<CR>
 nnoremap <C-t> :NERDTreeToggle<CR>
 highlight VertSplit cterm=none
+let NERDTreeShowHidden=1
 " Exit Vim if NERDTree is the only window remaining in the only tab.
 autocmd BufEnter * if tabpagenr('$') == 1 && winnr('$') == 1 && exists('b:NERDTree') && b:NERDTree.isTabTree() | quit | endif