Document the store's clock (timezone, utc_offset) on the Storefront API

[roncodes]

Summary

Documents the store's clock on the Storefront API, added in fleetbase/storefront release/v0.4.25 (959da71):

• Store (and a network from about with a network key): timezone, the store's IANA zone (its company's when the store has none), and utc_offset, its current offset from UTC in minutes, east positive.
• Food truck store: the same two fields.
• Cart items[].store: the same two fields.
• About Store: its description now says what it returns and how to read store hours and booked times on the store's clock (UTC + utc_offset) rather than the device's.

The console and the Storefront app (fleetbase/storefront-app#80) use these fields so that open/closed, booking slots and booked times read the same in every timezone.

Type of Change

• Bug fix
• Feature
• Refactor
• Documentation

Validation

node scripts/validate-collections.js: validated 5 collections and 3 environments.

Merge order

Merge after Storefront v0.4.25 is released; the fields come from that release.