Feature request: Creating overarching interface for all ui component models

I want to create an array of different bubbles UI components. The issue I've come across is that there is no great way to create an interface to group all of the components because each component exists as a separate package with each Model struct registered as separate type.

I was wondering why Init function isn't implemented for each component as such:

```go
func (m Model) Init() tea.Cmd {
return nil
}
```

And change the output type for the Update function:

```go
func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
...
}
```