[web] Introduce thread notification settings options in modal

Summary:
Introduce notification settings options in modal, that can be selected by the user.

Test Plan: The modal can be tested after introducing notification item in thread actions menu.

Reviewers: palys-swm, atul, benschac

Reviewed By: atul

Subscribers: ashoat, Adrian, atul, yayabosh

Differential Revision: https://phabricator.ashoat.com/D3953