Show release version in `Footer`

[fiskus]

• Get stack.version from GraphQL, show it in a footer; keep git revision for sentry and tracking

Also:

• Converted Notification.js and Footer.js to typescript
• Wrapped Footer and NavBar with ErrorBoundary: if they throw, the main content block could survive

I'm not sure about this approach. I would like to have version synchronously, but /config.js doesn't seem as a right place. Fetching version from GQL implies I don't have it for Sentry and tracking, because GraphQL initialized later. But, probably, it's ok to use version for UI and git hash for logs.

• [ ] Changelog entry (skip if change is not significant to end users, e.g. docs only)