[SIGs][meta-sig] Encourage SIG Chairs to join `Meet the project leaders` opportunities in Shanghai

Dear SIG chairs

There will be two `Meet the project leaders` event in Shanghai summit. And SIG chairs are definitely part of it. I'm here to encourage you to sign up [1] and join that event so people might get more chances to meet with you. They're scheduled on Monday marketplace mixer (5:30pm-7:00pm) and Wednesday lunch (12:20pm-1:40pm).

[1] https://etherpad.openstack.org/p/meet-the-project-leaders