Added easy-peasy global store

[dusanradovanovic]

Description:

This PR adds global state in the form of easy-peasy store. This global state will eventually be the only source of information for all user related info like authorization token, username, language selection etc. These information will be consumed by other components through the hooks that store exports.

Since other components are fetching and storing their own user info (like auth token) global store is currently implemented to "sync up" and follow that info through the system of events on window object. This mechanism will eventually be removed once all components that are using network calls are converted to functional components.

This also fixes the issue where user didn't see the navigation bar upon the first visit to the site.

Linting:

• No linting errors

Tests:

• E2E tests (npm test run with e2e)
• Manual tests
• Accessibility tests (no new react-axe errors in console)

Documentation:

• Requires documentation updates
• Requires Storybook component updates