Update rxdart to ^0.28.0 for improved compatibility

[bekzatzamirbekov]

Is your feature request related to a problem? Please describe.
Yes. The current version constraint for rxdart is ^0.27.0, which causes conflicts with other packages like bloc_lint that require rxdart ^0.28.0.

Describe the solution you'd like
Please consider updating the rxdart dependency to ^0.28.0, which is backwards compatible and resolves version conflicts.

Describe alternatives you've considered
I tried using dependency overrides, but it’s not ideal for long-term maintenance. It would be cleaner and safer to update it in the package directly.

Additional context
I'm happy to open a PR for this if preferred. Let me know!