Add 26.1 WPF docs for RangeBarSeries across chart and changelog topics

[Copilot]

This updates the WPF bar chart documentation for the new RangeBarSeries introduced in 26.1. It adds the feature to the active release documentation surfaces and mirrors the relevant content in Japanese.

• New chart topic

  • Added dedicated English and Japanese topics for RangeBarSeries
  • Documented:
    • series purpose and orientation vs. RangeColumnSeries
    • required axes (NumericXAxis + CategoryYAxis)
    • core member paths and legend-related properties
    • a minimal XAML example

• Release documentation

  • Added 26.1 changelog entries in English and Japanese calling out RangeBarSeries

• Related chart references

  • Updated the xamDataChart styling/reference topics to include RangeBarSeries alongside the other supported series types
  • Updated the new RangeBarSeries topics to reference the changelog as the release surface

• Docs consistency

  • Kept topic naming/linking aligned with existing datachart-* conventions
  • Corrected the nearby changelog TOC anchor for 25.2.107 while touching that section

<ig:XamDataChart>
    <ig:XamDataChart.Axes>
        <ig:NumericXAxis x:Name="xAxis" />
        <ig:CategoryYAxis x:Name="yAxis"
                          ItemsSource="{Binding}"
                          Label="{}{Label}" />
    </ig:XamDataChart.Axes>
    <ig:XamDataChart.Series>
        <ig:RangeBarSeries ItemsSource="{Binding}"
                           LowMemberPath="Low"
                           HighMemberPath="High"
                           XAxis="{Binding ElementName=xAxis}"
                           YAxis="{Binding ElementName=yAxis}" />
    </ig:XamDataChart.Series>
</ig:XamDataChart>

[IGvaleries]

same comment as other PRS that we haven't been using whats-new topics anymore and have just been using the changelog

[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 0d77a07.