[web] Open delete account modal after Delete Account button is clicked.
Summary:
Show a modal when user clicks the button.
Depends on D4119
Test Plan: Click the button and check if the modal was displayed. Close it by clicking outside and by clicking x button.
Reviewers: def-au1t, atul, benschac
Reviewed By: atul
Subscribers: ashoat, Adrian, yayabosh
Differential Revision: https://phabricator.ashoat.com/D4120