Feature/5.0.0 (#19)

* chore: Update dependencies and upgrade Flutter to Dart 2.12.0

* chore: Update platform import for JS interop compatibility

* chore: Update platform import for JS interop compatibility

* chore: Update platform import for JS interop compatibility

* chore: Update platform import for JS interop compatibility

* Rename test file

* chore: Update platform import for JS interop compatibility

* Update example.png

* Update example

Deploy config

Merge pull request #13 from PlugFox/develop

3.1.0

Merge remote-tracking branch 'origin/develop' into develop

Merge branch 'release/3.0.0-nullsafety.2'

Fix `kListOSWithCupertinoDesign` constant and `isCupertino` flag

fix pub bug