[web] Introduce Settings and Notifications thread menu actions

Summary:
Introduced Settings and Notifications actions in thread menu.
Currently, there are no modals displayed after clicking the button. I'll add onCLick action in follow-up diff.

Test Plan: Check if items are displayed correctly in every thread.

Reviewers: palys-swm, benschac, atul, ashoat

Reviewed By: palys-swm, ashoat

Subscribers: ashoat, palys-swm, Adrian, atul, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D3189