v2.0 Implementation

[aqwert]

The following is a list of TODOs for v2.0

• [x] Flutter 3.0 compatible
• [ ] Custom widget builders. This will allow a custom theme separate to material and cupertino. For example, it would be possible to create a bootstrap like design library (for web) or wrapped the MacosUI or FluentUI 3rd Party packages.
• [ ] ReadMe refresh
• [ ] Documentation of each platform widget (Tracked: https://github.com/stryder-dev/flutter_platform_widgets/issues/271), usage and examples
• [ ] Document any breaking changes
• [x] Remove deprecated fields
• [x] Remove PlatformButton which uses deprecated material FlatButton and RaisedButton. These are removed from flutter 3.1 so will need to be removed before that
• [ ] Any other minor enhancements

The above will get completed in time but should be released as part of a -dev package version. A version flutter 3.0 compatible version will likely go out with the PlatformButton to prepare for when flutter 3.10 is released (currently in beta)