feat(share_plus): Show destination for share with result in example, update example UI

[vbuberen]

Description

Saw that example app for share_plus shows only type of result in case with shareWithResult call, but not the destination. So adding a destination info as well to showcase the feature better for package users.

Additionally decided to give the example app UI a little visual improvement, so made it to use Material 3 and did small changes to make it look more modern and clean to use:

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.

[miquelbeltran]

LGTM, just left a comment on a possible improvement

[nohli]

Could be private