add recommendation about vagrantbox.es
add recommendation about vagrantbox.es

Signed-off-by: Hiroshi Miura <ff6fb3ed059786151e736af13627c08d24e9f922@linux.com>

vagrant-lists/vagrant-lists.github.io,vagrant-lists/vagrant-lists.github.io,virajs/vagrant-lists.github.io,virajs/vagrant-lists.github.io,vagrant-lists/vagrant-lists.github.io,virajs/vagrant-lists.github.io