Add an overview of Stack Exchange Redis caching

[IEvangelist]

Summary

• Add an overview of Stack Exchange Redis caching.
• Add TOC entry, and update Hub page.
• Fix brand name, should always have a space when referring to it by name (excluding NuGet package or namespace refs).

Fixes #1051

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Internal previews

📄 File	🔗 Preview link
docs/caching/caching-components-deployment.md	Tutorial: Deploy a .NET Aspire app with a Redis Cache to Azure
docs/caching/caching-components.md	Implement caching with .NET Aspire components
docs/caching/stackexchange-redis-caching-overview.md	Stack Exchange Redis caching overview
docs/caching/stackexchange-redis-component.md	docs/caching/stackexchange-redis-component
docs/caching/stackexchange-redis-distributed-caching-component.md	.NET Aspire Stack Exchange Redis distributed caching component
docs/caching/stackexchange-redis-output-caching-component.md	.NET Aspire Stack Exchange Redis output caching Component
docs/whats-new/dotnet-docs-aspire-mod1.md	.NET Aspire docs: What's new for April 2024
docs/whats-new/dotnet-docs-aspire-mod2.md	docs/whats-new/dotnet-docs-aspire-mod2