"What's new" improvements (#44638)

<!-- Enter a brief description/summary of your PR here. What does it
fix/what does it change/how was it tested (even manually, if necessary)?
-->
## Summary of the Pull Request

TO DO: Upgrade to the latest version of MarkdownTextBlock:
https://github.com/CommunityToolkit/Labs-Windows/pull/771

This PR introduces the following changes:
**Removed the custom titlebars on the OOBE Window, and replaced it with
the inbox WinUI `TitleBar` control.**

**New "What's new" experience following the VS Code release notes
experience**
- Created a new SCOOBE Windows that is a standalone window to better
visualize release notes.
- Adding a nav menu on the left to easily switch between release notes,
instead of a long page.
- Point releases are combined with the latest main release.. e.g. 0.96.1
is rendered above 0.96.0.
- The 'hero image' on main release notes will automatically be rendered
at the top of the page.
- Improved markdown styling for better readability.
- Pull requests links can now be clicked.
- Upgraded `CommunityToolkit.Labs.MarkdownTextblock` to the latest
version as it includes much needed bugfixes.

<img width="1234" height="819" alt="image"
src="https://github.com/user-attachments/assets/447b3136-306b-4f24-bc7a-c022a99e8e51"
/>

Note: the blurry image shown above will be replaced in new releases by
an image that fits the right dimensions.

<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist

- [ ] Closes: #xxx
<!-- - [ ] Closes: #yyy (add separate lines for additional resolved
issues) -->
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

---------

Co-authored-by: Leilei Zhang <leilzh@microsoft.com>

src/settings-ui/Settings.UI/SettingsXAML/ScoobeWindow.xaml

@@ -0,0 +1,17 @@
+<winuiex:WindowEx
+    x:Class="Microsoft.PowerToys.Settings.UI.ScoobeWindow"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:local="using:Microsoft.PowerToys.Settings.UI.OOBE.Views"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    xmlns:winuiex="using:WinUIEx"
+    MinWidth="480"
+    MinHeight="480"
+    Closed="Window_Closed"
+    mc:Ignorable="d">
+    <Window.SystemBackdrop>
+        <MicaBackdrop />
+    </Window.SystemBackdrop>
+    <local:ScoobeShellPage x:Name="shellPage" />
+</winuiex:WindowEx>