Enhance 1Password 8 manifest with iOS keys

[fspeirs]

Sorry about the earlier botched PR. This one should be more easily mergeable - it adds information about the keys supported by iOS and clarifies some of the text.

Is it OK to have an overall pfm_app_min at the top of the file, rather than having them in each item, given that all of these keys are supported on 8.9 and later on both platforms?

Also, I couldn't figure out how to have a different pfm_range_min value for different platforms for the key security.autolock.minutes. It should be 1 on macOS and 0 on iOS. I'm happy to adapt this PR if you can advise.

[apizz]

@fspeirs The idea is that the top-level pfm_app_min version in the manifest should reflect "high-level" minimum app version that supported management. As new preferences are added or are supported on different platforms, that's when you'd use the pfm_app_min at the preference level to indicate what's supported. That said, gaining iOS support for a set of preferences with pfm_app_min isn't possible on a per-OS basis, so I think the following is best:

1. Leave top-level pfm_app_min at 8.0.
2. For any existing preferences that were supported on macOS that are now also supported on iOS, leave the current pfm_app_min specified in the preference and add a pfm_note indicating what app version (8.9?) gained iOS support.
3. For new prefs that are only supported on iOS, add pfm_app_min at 8.9 for each of those preferences.

[apizz]

Per prev. comment