Update dependencies to their latest null safe version

[ashishbeck]

Hello, with the release of Flutter 2.0, the packages that this depends on need updating.
I have had conflicts with http and platform_interface so far. Could you please update the packages?
I could look into the code and create a PR if needed.

[mateusfccp]

@ashishbeck Thanks for contacting me!

I made a new publication 2.0.0-nullsafety. As I am not currently using Flutter 2.0 in production I don't have a proper setup to test this, but the code is properly migrated and all tests has passed.

Would you please try it for me? If you deem it working I will gladly publish it as stable (2.0.0).

[ashishbeck]

The package is compiling and building fine. There aren't any issues. I can't seem to check for updates locally in android, however. I think it's because I need to install from Google Play for the APIs to kick in. Regardless, the notAvailable function does work and I think it is okay to be published.
I have tested it for dev and release version.

[mateusfccp]

Thanks, @ashishbeck. Published 2.0.0 as stable. If you find any issue, please report it.