We can eliminate `OnboardingStep` component and pass content to each step using named slots. This seems more conventional in Vue - MW code like Codex than pairing/coupling components, eg: `<List>` and `<ListItem>`.
**Acceptance criteria**
- [] OnboardingStep component is removed
- [] OnboardingDialog can be used as it was with OnboardingStep but with an arbitrary number of steps: step1, step2... stepN
- [] AddLinkDialog does **not** need to know about `currentIndex` or step navigation handling
- [] OnboardingDialog emits events when there are navigation interactions and/or the `currentIndex` value changes so AddLinkDialog can subscribe to those events and instrument them
- [] AddLinkDialog **can** read the value of `currentIndex` or step navigation interactions through events
**Nice to have**
- [] OnboardingDialog can be used without any step and use the default slot to render some content on its body