Update TreeDataGrid documentation with notices and crosslinks to Accelerate#756

luke-whos-here merged 5 commits intomainAvaloniaUI/avalonia-docs:mainfrom

755-in-page-improving-performance-are-the-information-still-correctAvaloniaUI/avalonia-docs:755-in-page-improving-performance-are-the-information-still-correctCopy head branch name to clipboard