docs(share_plus): Add info regarding localization on Apple to README

[miquelbeltran]

Description

Improves the README.md adding an explanation on how to deal with different localizations and the share sheet on iOS.

Related Issues

• Related to On iOS, texts are not translated according to the phone's language #2696

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 plugin version in 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.

[vbuberen]

I remember some more issues about this, but they are closed now, I suppose
👍🏻