Document XAML Styler line ending expectations

[mortenn]

Summary

• document that the repository uses .gitattributes to preserve the line ending conventions XAML Styler expects on Windows
• provide a small smoke-test PR to verify the post-issue-258 PR validation workflow on a normal branch
• keep the change limited to docs so the PR is low risk

Test plan

• confirm the PR shows only the dedicated PR validation check
• confirm the PR validation run passes
• confirm the PR validation comment workflow posts or updates the summary comment

[github-actions]

PR Validation

Check	Result
CSharpier	success
XamlStyler	success
dotnet test	success

CSharpier

Output

Checked 59 files in 980ms.

XamlStyler

Output

Checking: src\BrowserPicker.UI\App.xaml
  PASS
Checking: src\BrowserPicker.UI\Resources\ResourceDictionary.xaml
  PASS
Checking: src\BrowserPicker.UI\Views\BrowserEditor.xaml
  PASS
Checking: src\BrowserPicker.UI\Views\BrowserList.xaml
  PASS
Checking: src\BrowserPicker.UI\Views\Configuration.xaml
  PASS
Checking: src\BrowserPicker.UI\Views\ExceptionReport.xaml
  PASS
Checking: src\BrowserPicker.UI\Views\LoadingWindow.xaml
  PASS
Checking: src\BrowserPicker.UI\Views\MainWindow.xaml
  PASS
Checking: src\BrowserPicker.UI\Views\UrlEditor.xaml
  PASS

9 of 9 files pass format check.

dotnet test

Output

  Determining projects to restore...
  Restored D:\a\BrowserPicker\BrowserPicker\src\BrowserPicker.UI\BrowserPicker.UI.csproj (in 9.63 sec).
  Restored D:\a\BrowserPicker\BrowserPicker\src\BrowserPicker.Common\BrowserPicker.Common.csproj (in 9.63 sec).
  Restored D:\a\BrowserPicker\BrowserPicker\src\BrowserPicker.Windows\BrowserPicker.Windows.csproj (in 9.63 sec).

Run: PR Validation #3