Widget for switching between C# and Rust code samples

[kazimuth]

This would be useful in documents that are not associated with a specific SDK language such as docs/index.md.

It would also be helpful if we can migrate existing documents that are duplicated between languages to single documents with switchable languages embedded. For example, it would be amazing if our module tutorials could switch between Rust and C# inline.

Requirements:

• Have contents for either:
  • All of our supported client languages
  • All of our supported server languages
• Synchronize with other such widgets on the page
  • Client-language-switcher widgets should synchronize with only other client-language-switcher-widgets, similarly for servers
  • Maybe should synchronize across the entire site?
• Support more than just a single code block inside; for example, tutorials might need to include console commands and documentation text that differ between languages.