Support null safety

[Sulisong]

would be great to have null safety enabled early

[tanersener]

I plan to support it when it is enabled in stable channel. Currently it is in beta.

[szymonmazanik]

Hello,
@tanersener as of yesterday the null safety is in stable channel. Could we kindly ask for migration?

Thanks!

[tanersener]

Will do when I find time. Feel free to submit PRs for it.

[zigyshop]

This will be awesome because of the release of Flutter 2.0. Right now, when using 2.0, the flutter package selection is impossible to override.

[nukes]

can version 0.3.1 run correctly with flutter 2.0 ? I cannot setup compilation on ios.

[tanersener]

@nukes yes, you can use it on Flutter 2.0. If you're using packages see #268

[shofizone]

Waiting for sound null safety !

[tanersener]

Thanks to @ibedek's PR, this is implemented in v0.4.0.