add mundo plugin

vimrc

@@ -31,6 +31,9 @@ Plug 'tpope/vim-fugitive'
 Plug 'tpope/vim-rhubarb'
 Plug 'airblade/vim-gitgutter'
 
+" undo
+Plug 'simnalamburt/vim-mundo'
+
 " appearence
 Plug 'itchyny/lightline.vim'
 Plug 'morhetz/gruvbox'
@@ -261,6 +264,9 @@ let g:ale_fixers = {
 \   'javascript': ['eslint'],
 \}
 
+"" undo
+nnoremap <leader>u :MundoToggle
+
 "" lightline
 if filereadable(expand("~/.vim/lightline.vim"))
     source ~/.vim/lightline.vim