Add Word chart cmdlets

[PrzemyslawKlys]

What changed

• add Add-OfficeWordChart for first-class Word chart generation in PSWriteOffice
• support pie, bar, line, and area charts from object data
• support chart insertion into open documents and paragraphs created inside table cells
• add docs and working chart examples

Why

This gives PSWriteOffice a real Word chart surface instead of relying only on raw OfficeIMO calls, and it closes the biggest chart-related gaps identified during issue review.

Validation

• dotnet build Sources/PSWriteOffice.sln
• Invoke-Pester Tests/WordDsl.Tests.ps1 -Output Detailed
  • Passed: 10

Notes

• Refs No Charts :( #7
• Refs PieChart method #19
• Supports the chart-in-cell path needed for Add Chart/Picture into Word Table Cell #3
• No issue-closing keywords yet because release is still pending.