Add document translation sample

[AhmadiRamin]

Add document translation sample

Provides document translation sample for SharePoint Framework. Users can select one or more documents from a SharePoint document library and translate them into multiple target languages simultaneously with real-time progress tracking.

Q	A
Bug fix?	no
New feature?	no
New sample?	yes

What's in this Pull Request?

This PR adds a new SharePoint Framework List View Command Set extension that enables users to translate documents from one language to another using Azure Document Translation Service.

Key Features:

• Multi-Language Translation: Translate documents to multiple target languages in a single operation
• Auto-Detect Source Language: Automatically detect the source language or manually specify it
• Batch Processing: Process multiple documents at once with configurable limits
• Real-Time Progress Monitoring: Track translation progress with live status updates
• Wide Format Support: Supports .docx, .xlsx, .pptx, .pdf, .html, .txt, .md, .msg, .odt, .ods, .odp
• Secure Authentication: Uses Azure AD OAuth 2.0 with On-Behalf-Of flow
• Comprehensive Error Handling: Per-document failure details and reporting
• Cost Transparency: Character count tracking for cost monitoring

What's Included:

• SPFx extension (v1.21.1) with React UI for document selection and language targeting
• Azure Function backend (.NET 9.0) for integration with Azure Translator Service
• Complete setup and configuration guides
• Detailed deployment instructions for SharePoint and Azure