feat(snacks): use snacks.dashboard as the default dashboard. moved dashboard-nvim to extras (#4832)

## Description

<!-- Describe the big picture of your changes to communicate to the
maintainers
  why we should accept this pull request. -->

Snacks has a new dashboard plugin that will be LazyVim's default.

Check the docs at
https://github.com/folke/snacks.nvim/blob/main/docs/dashboard.md

## Related Issue(s)

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  If this PR fixes any issues, please link to the issue here.
  - Fixes #<issue_number>
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## Screenshots

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## Checklist

- [x] I've read the
[CONTRIBUTING](https://github.com/LazyVim/LazyVim/blob/main/CONTRIBUTING.md)
guidelines.

NEWS.md

@@ -2,6 +2,13 @@
 
 ## 13.x
 
+- **LazyVim** now uses `Snacks.dashboard` as the default dashboard.
+  Check the [docs](https://github.com/folke/snacks.nvim/blob/main/docs/dashboard.md),
+  for more information and examples.
+
+- A new [dashboard-nvim](https://github.com/nvimdev/dashboard-nvim) extra
+  is available for those who prefer the old dashboard.
+
 - Big new release with a lot of changes and improvements!
 
 - The biggest change is the move of a bunch of core features to