This ext implements installer.
https://github.com/vim-denops/denops.vim
https://github.com/Shougo/dpp.vim
" Install plugins
call dpp#async_ext_action('installer', 'install')
" Update plugins
call dpp#async_ext_action('installer', 'update')
" Update dpp.vim
call dpp#async_ext_action('installer', 'update',
\ #{ names: ['dpp.vim'] })
" Check not updated plugins
call dpp#async_ext_action('installer', 'checkNotUpdated')
" Get not installed plugins
echo dpp#ext_action('installer', 'getNotInstalled')