Add WinForms 26.1 MarkerSize documentation across release notes and localized topics

[Copilot]

This updates the WinForms docs for the new chart MarkerSize property introduced in v26.1. The change covers release-note visibility and adds matching English/Japanese topic content so the feature is documented consistently across current discovery paths.

• Release notes

  • Added a new 26.1 (May 2026) entry to the English and Japanese changelogs
  • Documented the key MarkerSize behaviors:
    • explicit pixel sizing for marker-based series
    • NaN restoring template-driven sizing
    • support with lightweight markers
    • no effect on BubbleSeries radius-driven sizing

• What’s New content

  • Added new 2026 Volume 1 topics:
    • topics/en/whats-new-in-2026-volume-1.adoc
    • topics/ja/whats-new-in-2026-volume-1.ja-JP.adoc
  • Summarized usage, supported series, and the BubbleSeries exception

• Discovery / navigation

  • Added 2026 Volume 1 to revision history in both languages so the new topic is reachable from the standard “What’s New” navigation

Example snippet now reflected in the docs:

The link:{DataChartLink}.{DataChartName}.html[{DataChartName}] now supports a new `MarkerSize` property on series that render markers.

- restore the default template-driven marker size by setting the property to `NaN`

[NOTE]
====
`BubbleSeries` continues to size bubbles from its radius member path and `RadiusScale`, so `MarkerSize` does not override bubble radius values.
====

[gedinakova]

@copilot We should clarify that this sets device-independent pixels, not absolute pixel size. See this PR for reference. The docs were created with the old version that had an incorrect description.

https://github.com/Infragistics-Developer-Tools/dev-tools/pull/3485/changes#diff-6ffa07eb233cdb3c28af6c3a57699dd11433f54dd753f9bf151eca58ed0e6975R609

[Copilot]

Updated the wording to use device-independent pixels in the 2026 Volume 1 topic and the related changelog entries in both English and Japanese. Addressed in 3cdf6ef.