Add WinForms 26.1 Range Bar Series documentation and changelog updates

[Copilot]

Updates the WinForms bar chart documentation to cover the new RangeBarSeries introduced in 26.1. This adds the missing feature topic and the corresponding 26.1 changelog entries in both English and Japanese.

• New Range Bar Series topic

  • Added a new WinForms topic for RangeBarSeries in English and Japanese.
  • Covers:
    • series purpose and orientation
    • required axes (NumericXAxis + CategoryYAxis)
    • HighMemberPath / LowMemberPath
    • rendering behavior for horizontal range bars
    • commonly used properties such as RadiusX, RadiusY, and Data Legend label/unit settings
    • related links to existing bar/range topics

• Changelog updates

  • Added a 26.1 (2026) entry to the WinForms changelog in English and Japanese.
  • Documented RangeBarSeries as a new chart feature and linked to the new topic.

• Example usage

  var xAxis = new NumericXAxis();
  var yAxis = new CategoryYAxis();
  yAxis.DataSource = data;
  yAxis.Label = "{Country}";
  
  var series = new RangeBarSeries();
  series.DataSource = data;
  series.HighMemberPath = "Coal";
  series.LowMemberPath = "Oil";
  series.XAxis = xAxis;
  series.YAxis = yAxis;

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[IGvaleries]

Same comment again we no longer doing "what's new" docs.
we also stopped adding VB code snippets, but that's just an FYI, since they are heer I don't see any need to remove them

Also, not sure if that datasource was the best to demonstrate how the chart might actually be used but I guess it is OK

[gedinakova]

@copilot Delete the newly added what's new topics (both english and japanese) as they are no longer used.

[Copilot]

@copilot Delete the newly added what's new topics (both english and japanese) as they are no longer used.

Addressed in 4f625a1.