[web] Dispatch change notification settings action in NotificationsModal

Summary: Dispatch server action after clicking on save button in the notifications modal

Test Plan: Checked if the notifications settings are changed after selecting different options (e.g. by checking the tab - focus/selected)

Reviewers: palys-swm, benschac, atul

Reviewed By: atul

Subscribers: ashoat, Adrian, atul, yayabosh

Differential Revision: https://phabricator.ashoat.com/D3954