C#: add docs #2574

Job	Run time
Check	1m 57s
Rustfmt	4s
Build wit-bindgen (x86_64-linux, ubuntu-latest)	1m 30s
Test (ubuntu-latest, c)	4m 18s
Build wit-bindgen (x86_64-macos, macos-latest, x86_64-apple-darwin)	1m 26s
Crate Unit Tests	55s
Test (ubuntu-latest, rust)	4m 42s
verify-publish	1m 45s
Build wit-bindgen (aarch64-macos, macos-latest, aarch64-apple-darwin)	1m 33s
Test (ubuntu-latest, teavm-java)	4m 55s
Build wit-bindgen (x86_64-windows, windows-latest)	4m 42s
Test (ubuntu-latest, go)	5m 36s
Build wit-bindgen (aarch64-linux, ubuntu-latest, aarch64-unknown-linux-gnu)	1m 45s
Test (ubuntu-latest, csharp)	8m 0s
Test (macos-latest, c)	6m 50s
Test (macos-latest, rust)	5m 18s
Test (macos-latest, teavm-java)	4m 37s
Test (macos-latest, go)	5m 28s
Test (macos-latest, csharp)	8m 10s
Test (windows-latest, c)	8m 24s
Test (windows-latest, rust)	10m 18s
Test (windows-latest, teavm-java)	9m 18s
Test (windows-latest, go)	10m 51s
Test (windows-latest, csharp)	32m 18s
Record the result of testing and building steps	1s
	2h 24m 41s

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