[Feat] Add optional initial value arguments to useNetworkStatus, useSaveData; useMemoryStatus

[mlampedx]

Purpose:

I am proposing that we add an optional initial value argument to the useNetworkStatus, useSaveData, and useMemoryStatus hooks to enable the developer to provide an alternative source for this valuable data in the event that the JavaScript runtime environment/the user's browser lacks the required APIs.

This opens up the opportunity for developers to utilize relevant server-side client hints that are available. For example, in instances where the server-side client hint value is reliable and consistent with the navigator value, populating the useNetworkStatus hook on the server can enable adaptive loading on SSR, reduce re-renders, and ensure HTML is consistent between SSR and client-side hydration.

Completed:

• Add optional initial value arguments to useNetworkStatus, useSaveData; useMemoryStatus
• Add unsupported property to all states returned by hooks for consistency
• Bolster test coverage to 100%
• Update documentation to include references to the initial value arguments as well as use cases

Please let me know if you would like me to amend, revert, or clarify any of the changes that I am proposing 😄

[addyosmani]

Overall this implementation looks great. Thank you for working on initial value support and the corresponding tests, @mlampedx!

I would love for us to check how far this addresses @gja's original concerns in #18 and sanity check how we might want to factor in #18 (comment) or #18 (comment). I think it's completely fair if we address the rest of attribute mismatch in a separate PR, but a brief discussion before landing this is probably healthy :)

[addyosmani]

Initial work LGTM with minor comments.

[mlampedx]

Thank you, @addyosmani ! I have addressed your comments and followed up on the original issue thread.

[addyosmani]

Thank you, @mlampedx. I think there's enough value in the initial value arguments implementation here for us to land it and then make a decision on the right design for the second half of the problem over in #18. Approving and landing shortly 🚀

[addyosmani]

LGTM