Windows, macOS, and Linux Support

[jhancock4d]

Is your feature request related to a problem? Please describe.
Right now, this is the only plugin that is blocking us from release for desktop. Please consider adding support for windows, linux and macOS.

Describe the solution you'd like
macOS and Linux should just return false as they don't have real touch support natively, and windows should handle the soft keyboard.

[cbenhagen]

I added a PR with desktop implementations which return false. If you want to use them before the PR is merged you can do so by adding the following to your pubspec.yaml:

  flutter_keyboard_visibility_linux:
    git:
      url: https://github.com/cbenhagen/flutter_keyboard_visibility/
      ref: desktop
      path: flutter_keyboard_visibility_linux
  flutter_keyboard_visibility_macos:
    git:
      url: https://github.com/cbenhagen/flutter_keyboard_visibility/
      ref: desktop
      path: flutter_keyboard_visibility_macos
  flutter_keyboard_visibility_windows:
    git:
      url: https://github.com/cbenhagen/flutter_keyboard_visibility/
      ref: desktop
      path: flutter_keyboard_visibility_windows

[jhancock4d]

Note that false isn't valid for Windows in tablet mode as it may or may not be displayed and thus needs to use the API to get it's status.

I think the same is true under Linux although I'm not sure that there is a standardized API for it. (Ubuntu Touch and others)

Obviously Mac is always false for now.

[MisterJimson]

I think a good first release that just returns false to unblock folks is appropriate. Same as was done for web.

Then a proper implementation can follow.

[cbenhagen]

Sorry for the confusion. Yes this is only a stub to get rid of the error messages and make it easier to implement on each platform. MacOS actually has the accessibility keyboard of which we might want to know if it is visible.