Analyzer equivalent to must_use on Result

[jtmueller]

Is your feature request related to a problem? Please describe.

Rust defines the #[must_use] attribute on the Result type so that the compiler gives a warning if you forget to check the return value from a Result-returning function. Currently RustyOptions does not do this, making it easy to forget this crucial step.

https://doc.rust-lang.org/std/result/#results-must-be-used

Describe the solution you'd like
C# doesn't have must_use, but it might be possible to create an analyzer that does the same thing.

[jtmueller]

Basic tutorial:
https://devblogs.microsoft.com/dotnet/how-to-write-a-roslyn-analyzer/

IDisposable Analyzers has an analyzer very similar to what we need for Result here:
https://github.com/DotNetAnalyzers/IDisposableAnalyzers/blob/master/IDisposableAnalyzers/Analyzers/CreationAnalyzer.cs