[web] Send platform details on websocket connection

Summary:
Now it makes sense to send it on websocket connection to update the server on the web app version.

Depends on D7854

Test Plan:
Run production version of the web app so there's no hot reloading.

• run the web app, check the db cookie table if it has no version
• update registerConfig in app.react.js to contain platformDetails with the version
• reload the web app, check if there's new version in the db

Reviewers: kamil, tomek

Reviewed By: tomek

Subscribers: ashoat, atul

Differential Revision: https://phab.comm.dev/D7855