[web] Validate website responder

Summary:
Validate website responder by adding an intial redux state validator. It's not a full (Web)AppState validator because we don't need it for this purpose.

Depends on D7785

Test Plan: Load the web app and check if there were any errors. Repeat with a few other accounts.

Reviewers: kamil, tomek

Reviewed By: tomek

Subscribers: ashoat, atul

Differential Revision: https://phab.comm.dev/D7786