Remove reachability dependency

[HenriBeck]

I'm not quite sure why Reachability was a dependency but removing it didn't cause any issues for me.

[MisterJimson]

This is causing issues for me as other libs depend on ReachabilitySwift and during release builds linking can fail with conflicts.

[HenriBeck]

@MisterJimson

For now, you could use this:

  keyboard_visibility:
    git:
      url: https://github.com/HenriBeck/flutter_keyboard_visibility.git
      ref: 1f87a4b7797df567f63a3248ee7ed7aa0179f35b

[MisterJimson]

Hey I would really like to see this merged. While we can use a forked version, that does not work well for other packages that depend on this lib. Let me know if there is anything I can do to help.

[mixdesign]

@adee42 Would you review the suggested merge request? Thank you

[MisterJimson]

FYI I pulled this bug fix into my fork if you want to use it: https://github.com/MisterJimson/flutter_keyboard_visibility