docs(device_info_plus): Add info about Android properties availability, update API docs links

[vbuberen]

Description

Adding more info to some of AndroidDeviceInfo properties, so it is clear which properties might be null on some older platforms.

Saw that links to API documentation on the website and README redirected users just to pub.dev page of the device_info_plus, so updated the link. Also added the same link to the Overview page explaining to users that they can find the full list of properties there.

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I titled the PR using Conventional Commits.
• I did not modify the CHANGELOG.md nor the pubspec.yaml files.
• All existing and new tests are passing.
• The analyzer (flutter analyze) does not report any problems on my PR.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change (please indicate that with a ! in the title as explained in Conventional Commits).
• No, this is not a breaking change.

[github-actions]

Visit the preview URL for this PR (updated for commit 7640ba8):

https://flutter-community-plus--pr1243-update-docs-device-i-rm62s3ff.web.app

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[nohli]

🚀