[web] introduce CommunitiesRefresher

Summary:
As mentioned in D11995 we want to call the fetch_community_infos endpoint whenever the browser window becomes active. CommunitiesRefresher is a component that handles this logic

Linear task: https://linear.app/comm/issue/ENG-7942/introduce-communityinforefresher-for-web

Depends on D11996

Test Plan: Confirmed that we were calling fetch_community_infos whenever the browser window becomes active

Reviewers: tomek, kamil

Reviewed By: tomek

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D11997