Add page view analytics integration instructions

[defagos]

As a developer integrating Pillarbox I want to be informed how page view analytics can be best integrating into my application.

Acceptance criteria

• Page view integration for CarPlay is documented.
• Split view page view measurements is documented.

Tasks

• [x] ~Document CarPlay measurements.~
• [x] ~Document split view measurements.~

Hints

See https://github.com/SRGSSR/pillarbox-documentation/issues/25.

[defagos]

Moved to #355 since the main analytics documentation is missing.