## Migration guide from 0.60.0 to 0.61.0
- `MSG` is now an associated type to `Application`
- `Cmd<Self>` should now be just `Cmd<Msg>`
old:
```rust
impl Application<Msg> for App{
fn update(&mut self, msg: Msg) -> Cmd<Self> {
...
}
}
```
new:
```rust
impl Application for App {
type MSG = Msg;
fn update(&mut self, msg: Msg) -> Cmd<Msg>{
...
}
}
```